/* * Copyright (c) 1994, 2025, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.Console; import java.io.FileDescriptor; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.PrintStream; import java.lang.annotation.Annotation; import java.lang.foreign.MemorySegment; import java.lang.invoke.MethodHandle; import java.lang.invoke.MethodType; import java.lang.module.ModuleDescriptor; import java.lang.reflect.Executable; import java.lang.reflect.Method; import java.net.URI; import java.nio.channels.Channel; import java.nio.channels.spi.SelectorProvider; import java.nio.charset.CharacterCodingException; import java.nio.charset.Charset; import java.security.ProtectionDomain; import java.util.List; import java.util.Locale; import java.util.Map; import java.util.Objects; import java.util.Properties; import java.util.ResourceBundle; import java.util.Set; import java.util.concurrent.Executor; import java.util.concurrent.ScheduledExecutorService; import java.util.function.Supplier; import java.util.concurrent.ConcurrentHashMap; import java.util.stream.Stream; import jdk.internal.javac.Restricted; import jdk.internal.loader.NativeLibraries; import jdk.internal.logger.LoggerFinderLoader.TemporaryLoggerFinder; import jdk.internal.misc.Blocker; import jdk.internal.misc.CarrierThreadLocal; import jdk.internal.util.StaticProperty; import jdk.internal.module.ModuleBootstrap; import jdk.internal.module.ServicesCatalog; import jdk.internal.reflect.CallerSensitive; import jdk.internal.reflect.Reflection; import jdk.internal.access.JavaLangAccess; import jdk.internal.access.SharedSecrets; import jdk.internal.logger.LoggerFinderLoader; import jdk.internal.logger.LazyLoggers; import jdk.internal.logger.LocalizedLoggerWrapper; import jdk.internal.misc.VM; import jdk.internal.util.SystemProps; import jdk.internal.vm.Continuation; import jdk.internal.vm.ContinuationScope; import jdk.internal.vm.StackableScope; import jdk.internal.vm.ThreadContainer; import jdk.internal.vm.annotation.IntrinsicCandidate; import jdk.internal.vm.annotation.Stable; import sun.reflect.annotation.AnnotationType; import sun.nio.ch.Interruptible; import sun.nio.cs.UTF_8; /** * The {@code System} class contains several useful class fields * and methods. It cannot be instantiated. * * Among the facilities provided by the {@code System} class * are standard input, standard output, and error output streams; * access to externally defined properties and environment * variables; a means of loading files and libraries; and a utility * method for quickly copying a portion of an array. * * @since 1.0 */ public final class System { /* Register the natives via the static initializer. * * The VM will invoke the initPhase1 method to complete the initialization * of this class separate from . */ private static native void registerNatives(); static { registerNatives(); } /** Don't let anyone instantiate this class */ private System() { } /** * The "standard" input stream. This stream is already * open and ready to supply input data. This stream * corresponds to keyboard input or another input source specified by * the host environment or user. Applications should use the encoding * specified by the {@link ##stdin.encoding stdin.encoding} property * to convert input bytes to character data. * * @apiNote * The typical approach to read character data is to wrap {@code System.in} * within the object that handles character encoding. After this is done, * subsequent reading should use only the wrapper object; continuing to * operate directly on {@code System.in} results in unspecified behavior. *

* Here are two common examples. Using an {@link java.io.InputStreamReader * InputStreamReader}: * {@snippet lang=java : * new InputStreamReader(System.in, System.getProperty("stdin.encoding")); * } * Or using a {@link java.util.Scanner Scanner}: * {@snippet lang=java : * new Scanner(System.in, System.getProperty("stdin.encoding")); * } *

* For handling interactive input, consider using {@link Console}. * * @see Console * @see ##stdin.encoding stdin.encoding */ public static final InputStream in = null; /** * The "standard" output stream. This stream is already * open and ready to accept output data. Typically this stream * corresponds to display output or another output destination * specified by the host environment or user. The encoding used * in the conversion from characters to bytes is equivalent to * {@link ##stdout.encoding stdout.encoding}. *

* For simple stand-alone Java applications, a typical way to write * a line of output data is: * 

     *     System.out.println(data)
     *
*

* See the {@code println} methods in class {@code PrintStream}. * * @see java.io.PrintStream#println() * @see java.io.PrintStream#println(boolean) * @see java.io.PrintStream#println(char) * @see java.io.PrintStream#println(char[]) * @see java.io.PrintStream#println(double) * @see java.io.PrintStream#println(float) * @see java.io.PrintStream#println(int) * @see java.io.PrintStream#println(long) * @see java.io.PrintStream#println(java.lang.Object) * @see java.io.PrintStream#println(java.lang.String) * @see ##stdout.encoding stdout.encoding */ public static final PrintStream out = null; /** * The "standard" error output stream. This stream is already * open and ready to accept output data. *

* Typically this stream corresponds to display output or another * output destination specified by the host environment or user. By * convention, this output stream is used to display error messages * or other information that should come to the immediate attention * of a user even if the principal output stream, the value of the * variable {@code out}, has been redirected to a file or other * destination that is typically not continuously monitored. * The encoding used in the conversion from characters to bytes is * equivalent to {@link ##stderr.encoding stderr.encoding}. * * @see ##stderr.encoding stderr.encoding */ public static final PrintStream err = null; // Initial values of System.in and System.err, set in initPhase1(). private static @Stable InputStream initialIn; private static @Stable PrintStream initialErr; // `sun.jnu.encoding` if it is not supported. Otherwise null. // It is initialized in `initPhase1()` before any charset providers // are initialized. private static String notSupportedJnuEncoding; /** * Reassigns the "standard" input stream. * * @param in the new standard input stream. * * @since 1.1 */ public static void setIn(InputStream in) { setIn0(in); } /** * Reassigns the "standard" output stream. * * @param out the new standard output stream * * @since 1.1 */ public static void setOut(PrintStream out) { setOut0(out); } /** * Reassigns the "standard" error output stream. * * @param err the new standard error output stream. * * @since 1.1 */ public static void setErr(PrintStream err) { setErr0(err); } private static volatile Console cons; /** * Returns the unique {@link java.io.Console Console} object associated * with the current Java virtual machine, if any. * * @return The system console, if any, otherwise {@code null}. * * @since 1.6 */ public static Console console() { Console c; if ((c = cons) == null) { synchronized (System.class) { if ((c = cons) == null) { cons = c = SharedSecrets.getJavaIOAccess().console(); } } } return c; } /** * Returns the channel inherited from the entity that created this * Java virtual machine. * * This method returns the channel obtained by invoking the * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel * inheritedChannel} method of the system-wide default * {@link java.nio.channels.spi.SelectorProvider} object. * *

In addition to the network-oriented channels described in * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel * inheritedChannel}, this method may return other kinds of * channels in the future. * * @return The inherited channel, if any, otherwise {@code null}. * * @throws IOException * If an I/O error occurs * * @since 1.5 */ public static Channel inheritedChannel() throws IOException { return SelectorProvider.provider().inheritedChannel(); } private static native void setIn0(InputStream in); private static native void setOut0(PrintStream out); private static native void setErr0(PrintStream err); /** * Throws {@code UnsupportedOperationException}. Setting a security manager * is not supported. * * @param sm ignored * @throws UnsupportedOperationException always * @see #getSecurityManager * @deprecated This method originally set * {@linkplain SecurityManager the system-wide Security Manager}. * Setting a Security Manager is no longer supported. There is no * replacement for the Security Manager or this method. */ @Deprecated(since="17", forRemoval=true) public static void setSecurityManager(@SuppressWarnings("removal") SecurityManager sm) { throw new UnsupportedOperationException( "Setting a Security Manager is not supported"); } /** * Returns {@code null}. Setting a security manager is not supported. * * @return {@code null} * @see #setSecurityManager * @deprecated This method originally returned * {@linkplain SecurityManager the system-wide Security Manager}. * Setting a Security Manager is no longer supported. There is no * replacement for the Security Manager or this method. */ @SuppressWarnings("removal") @Deprecated(since="17", forRemoval=true) public static SecurityManager getSecurityManager() { return null; } /** * Returns the current time in milliseconds. Note that * while the unit of time of the return value is a millisecond, * the granularity of the value depends on the underlying * operating system and may be larger. For example, many * operating systems measure time in units of tens of * milliseconds. * *

See the description of the class {@code Date} for * a discussion of slight discrepancies that may arise between * "computer time" and coordinated universal time (UTC). * * @return the difference, measured in milliseconds, between * the current time and midnight, January 1, 1970 UTC. * @see java.util.Date */ @IntrinsicCandidate public static native long currentTimeMillis(); /** * Returns the current value of the running Java Virtual Machine's * high-resolution time source, in nanoseconds. * * This method can only be used to measure elapsed time and is * not related to any other notion of system or wall-clock time. * The value returned represents nanoseconds since some fixed but * arbitrary origin time (perhaps in the future, so values * may be negative). The same origin is used by all invocations of * this method in an instance of a Java virtual machine; other * virtual machine instances are likely to use a different origin. * *

This method provides nanosecond precision, but not necessarily * nanosecond resolution (that is, how frequently the value changes) * - no guarantees are made except that the resolution is at least as * good as that of {@link #currentTimeMillis()}. * *

Differences in successive calls that span greater than * approximately 292 years (263 nanoseconds) will not * correctly compute elapsed time due to numerical overflow. * *

The values returned by this method become meaningful only when * the difference between two such values, obtained within the same * instance of a Java virtual machine, is computed. * *

For example, to measure how long some code takes to execute: * 

 {@code
     * long startTime = System.nanoTime();
     * // ... the code being measured ...
     * long elapsedNanos = System.nanoTime() - startTime;}
* *

To compare elapsed time against a timeout, use 

 {@code
     * if (System.nanoTime() - startTime >= timeoutNanos) ...}
* instead of 
 {@code
     * if (System.nanoTime() >= startTime + timeoutNanos) ...}
* because of the possibility of numerical overflow. * * @return the current value of the running Java Virtual Machine's * high-resolution time source, in nanoseconds * @since 1.5 */ @IntrinsicCandidate public static native long nanoTime(); /** * Copies an array from the specified source array, beginning at the * specified position, to the specified position of the destination array. * A subsequence of array components are copied from the source * array referenced by {@code src} to the destination array * referenced by {@code dest}. The number of components copied is * equal to the {@code length} argument. The components at * positions {@code srcPos} through * {@code srcPos+length-1} in the source array are copied into * positions {@code destPos} through * {@code destPos+length-1}, respectively, of the destination * array. *

* If the {@code src} and {@code dest} arguments refer to the * same array object, then the copying is performed as if the * components at positions {@code srcPos} through * {@code srcPos+length-1} were first copied to a temporary * array with {@code length} components and then the contents of * the temporary array were copied into positions * {@code destPos} through {@code destPos+length-1} of the * destination array. *

* If {@code dest} is {@code null}, then a * {@code NullPointerException} is thrown. *

* If {@code src} is {@code null}, then a * {@code NullPointerException} is thrown and the destination * array is not modified. *

* Otherwise, if any of the following is true, an * {@code ArrayStoreException} is thrown and the destination is * not modified: *

*

* Otherwise, if any of the following is true, an * {@code IndexOutOfBoundsException} is * thrown and the destination is not modified: *

*

* Otherwise, if any actual component of the source array from * position {@code srcPos} through * {@code srcPos+length-1} cannot be converted to the component * type of the destination array by assignment conversion, an * {@code ArrayStoreException} is thrown. In this case, let * k be the smallest nonnegative integer less than * length such that {@code src[srcPos+}k{@code ]} * cannot be converted to the component type of the destination * array; when the exception is thrown, source array components from * positions {@code srcPos} through * {@code srcPos+}k{@code -1} * will already have been copied to destination array positions * {@code destPos} through * {@code destPos+}k{@code -1} and no other * positions of the destination array will have been modified. * (Because of the restrictions already itemized, this * paragraph effectively applies only to the situation where both * arrays have component types that are reference types.) * * @param src the source array. * @param srcPos starting position in the source array. * @param dest the destination array. * @param destPos starting position in the destination data. * @param length the number of array elements to be copied. * @throws IndexOutOfBoundsException if copying would cause * access of data outside array bounds. * @throws ArrayStoreException if an element in the {@code src} * array could not be stored into the {@code dest} array * because of a type mismatch. * @throws NullPointerException if either {@code src} or * {@code dest} is {@code null}. */ @IntrinsicCandidate public static native void arraycopy(Object src, int srcPos, Object dest, int destPos, int length); /** * Returns the same hash code for the given object as * would be returned by the default method hashCode(), * whether or not the given object's class overrides * hashCode(). * The hash code for the null reference is zero. * * @param x object for which the hashCode is to be calculated * @return the hashCode * @since 1.1 * @see Object#hashCode * @see java.util.Objects#hashCode(Object) */ @IntrinsicCandidate public static native int identityHashCode(Object x); /** * System properties. * * See {@linkplain #getProperties getProperties} for details. */ private static Properties props; /** * Determines the current system properties. *

* The current set of system properties for use by the * {@link #getProperty(String)} method is returned as a * {@code Properties} object. If there is no current set of * system properties, a set of system properties is first created and * initialized. This set of system properties includes a value * for each of the following keys unless the description of the associated * value indicates that the value is optional. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Shows property keys and associated values
KeyDescription of Associated Value
{@systemProperty java.version}Java Runtime Environment version, which may be interpreted * as a {@link Runtime.Version}
{@systemProperty java.version.date}Java Runtime Environment version date, in ISO-8601 YYYY-MM-DD * format, which may be interpreted as a {@link * java.time.LocalDate}
{@systemProperty java.vendor}Java Runtime Environment vendor
{@systemProperty java.vendor.url}Java vendor URL
{@systemProperty java.vendor.version}Java vendor version (optional)
{@systemProperty java.home}Java installation directory
{@systemProperty java.vm.specification.version}Java Virtual Machine specification version, whose value is the * {@linkplain Runtime.Version#feature feature} element of the * {@linkplain Runtime#version() runtime version}
{@systemProperty java.vm.specification.vendor}Java Virtual Machine specification vendor
{@systemProperty java.vm.specification.name}Java Virtual Machine specification name
{@systemProperty java.vm.version}Java Virtual Machine implementation version which may be * interpreted as a {@link Runtime.Version}
{@systemProperty java.vm.vendor}Java Virtual Machine implementation vendor
{@systemProperty java.vm.name}Java Virtual Machine implementation name
{@systemProperty java.specification.version}Java Runtime Environment specification version, whose value is * the {@linkplain Runtime.Version#feature feature} element of the * {@linkplain Runtime#version() runtime version}
{@systemProperty java.specification.maintenance.version}Java Runtime Environment specification maintenance version, * may be interpreted as a positive integer (optional, see below)
{@systemProperty java.specification.vendor}Java Runtime Environment specification vendor
{@systemProperty java.specification.name}Java Runtime Environment specification name
{@systemProperty java.class.version}{@linkplain java.lang.reflect.ClassFileFormatVersion#latest() Latest} * Java class file format version recognized by the Java runtime as {@code "MAJOR.MINOR"} * where {@link java.lang.reflect.ClassFileFormatVersion#major() MAJOR} and {@code MINOR} * are both formatted as decimal integers
{@systemProperty java.class.path}Java class path (refer to * {@link ClassLoader#getSystemClassLoader()} for details)
{@systemProperty java.library.path}List of paths to search when loading libraries
{@systemProperty java.io.tmpdir}Default temp file path
{@systemProperty os.name}Operating system name
{@systemProperty os.arch}Operating system architecture
{@systemProperty os.version}Operating system version
{@systemProperty file.separator}File separator ("/" on UNIX)
{@systemProperty path.separator}Path separator (":" on UNIX)
{@systemProperty line.separator}Line separator ("\n" on UNIX)
{@systemProperty user.name}User's account name
{@systemProperty user.home}User's home directory
{@systemProperty user.dir}User's current working directory
{@systemProperty native.encoding}Character encoding name derived from the host environment and * the user's settings. Setting this system property on the command line * has no effect.
{@systemProperty stdin.encoding}Character encoding name for {@link System#in System.in}. * The Java runtime can be started with the system property set to {@code UTF-8}. * Starting it with the property set to another value results in unspecified behavior. *
{@systemProperty stdout.encoding}Character encoding name for {@link System#out System.out} and * {@link System#console() System.console()}. * The Java runtime can be started with the system property set to {@code UTF-8}. * Starting it with the property set to another value results in unspecified behavior. *
{@systemProperty stderr.encoding}Character encoding name for {@link System#err System.err}. * The Java runtime can be started with the system property set to {@code UTF-8}. * Starting it with the property set to another value results in unspecified behavior. *
*

* The {@code java.specification.maintenance.version} property is * defined if the specification implemented by this runtime at the * time of its construction had undergone a maintenance * release. When defined, its value identifies that * maintenance release. To indicate the first maintenance release * this property will have the value {@code "1"}, to indicate the * second maintenance release this property will have the value * {@code "2"}, and so on. *

* Multiple paths in a system property value are separated by the path * separator character of the platform. *

* Additional locale-related system properties defined by the * {@link Locale##default_locale Default Locale} section in the {@code Locale} * class description may also be obtained with this method. * * @apiNote * Changing a standard system property may have unpredictable results * unless otherwise specified. * Property values may be cached during initialization or on first use. * Setting a standard property after initialization using {@link #getProperties()}, * {@link #setProperties(Properties)}, {@link #setProperty(String, String)}, or * {@link #clearProperty(String)} may not have the desired effect. * * @implNote * In addition to the standard system properties, the system * properties may include the following keys: * * * * * * * * * * * * * * * * * * *
Shows property keys and associated values
KeyDescription of Associated Value
{@systemProperty jdk.module.path}The application module path
{@systemProperty jdk.module.upgrade.path}The upgrade module path
{@systemProperty jdk.module.main}The module name of the initial/main module
{@systemProperty jdk.module.main.class}The main class name of the initial module
{@systemProperty file.encoding}The name of the default charset, defaults to {@code UTF-8}. * The property may be set on the command line to the value * {@code UTF-8} or {@code COMPAT}. If set on the command line to * the value {@code COMPAT} then the value is replaced with the * value of the {@code native.encoding} property during startup. * Setting the property to a value other than {@code UTF-8} or * {@code COMPAT} results in unspecified behavior. *
* * @return the system properties * @see #setProperties * @see java.util.Properties */ public static Properties getProperties() { return props; } /** * Returns the system-dependent line separator string. It always * returns the same value - the initial value of the {@linkplain * #getProperty(String) system property} {@code line.separator}. * *

On UNIX systems, it returns {@code "\n"}; on Microsoft * Windows systems it returns {@code "\r\n"}. * * @return the system-dependent line separator string * @since 1.7 */ public static String lineSeparator() { return lineSeparator; } private static String lineSeparator; /** * Sets the system properties to the {@code Properties} argument. *

* The argument becomes the current set of system properties for use * by the {@link #getProperty(String)} method. If the argument is * {@code null}, then the current set of system properties is * forgotten. * * @apiNote * Changing a standard system property may have unpredictable results * unless otherwise specified. * See {@linkplain #getProperties getProperties} for details. * * @param props the new system properties. * @see #getProperties * @see java.util.Properties */ public static void setProperties(Properties props) { if (props == null) { Map tempProps = SystemProps.initProperties(); VersionProps.init(tempProps); props = createProperties(tempProps); } System.props = props; } /** * Gets the system property indicated by the specified key. *

* If there is no current set of system properties, a set of system * properties is first created and initialized in the same manner as * for the {@code getProperties} method. * * @apiNote * Changing a standard system property may have unpredictable results * unless otherwise specified. * See {@linkplain #getProperties getProperties} for details. * * @param key the name of the system property. * @return the string value of the system property, * or {@code null} if there is no property with that key. * * @throws NullPointerException if {@code key} is {@code null}. * @throws IllegalArgumentException if {@code key} is empty. * @see #setProperty * @see java.lang.System#getProperties() */ public static String getProperty(String key) { checkKey(key); return props.getProperty(key); } /** * Gets the system property indicated by the specified key. *

* If there is no current set of system properties, a set of system * properties is first created and initialized in the same manner as * for the {@code getProperties} method. * * @param key the name of the system property. * @param def a default value. * @return the string value of the system property, * or the default value if there is no property with that key. * * @throws NullPointerException if {@code key} is {@code null}. * @throws IllegalArgumentException if {@code key} is empty. * @see #setProperty * @see java.lang.System#getProperties() */ public static String getProperty(String key, String def) { checkKey(key); return props.getProperty(key, def); } /** * Sets the system property indicated by the specified key. * * @apiNote * Changing a standard system property may have unpredictable results * unless otherwise specified. * See {@linkplain #getProperties getProperties} for details. * * @param key the name of the system property. * @param value the value of the system property. * @return the previous value of the system property, * or {@code null} if it did not have one. * * @throws NullPointerException if {@code key} or * {@code value} is {@code null}. * @throws IllegalArgumentException if {@code key} is empty. * @see #getProperty * @see java.lang.System#getProperty(java.lang.String) * @see java.lang.System#getProperty(java.lang.String, java.lang.String) * @since 1.2 */ public static String setProperty(String key, String value) { checkKey(key); return (String) props.setProperty(key, value); } /** * Removes the system property indicated by the specified key. * * @apiNote * Changing a standard system property may have unpredictable results * unless otherwise specified. * See {@linkplain #getProperties getProperties} method for details. * * @param key the name of the system property to be removed. * @return the previous string value of the system property, * or {@code null} if there was no property with that key. * * @throws NullPointerException if {@code key} is {@code null}. * @throws IllegalArgumentException if {@code key} is empty. * @see #getProperty * @see #setProperty * @see java.util.Properties * @since 1.5 */ public static String clearProperty(String key) { checkKey(key); return (String) props.remove(key); } private static void checkKey(String key) { if (key == null) { throw new NullPointerException("key can't be null"); } if (key.isEmpty()) { throw new IllegalArgumentException("key can't be empty"); } } /** * Gets the value of the specified environment variable. An * environment variable is a system-dependent external named * value. * *

System * properties and environment variables are both * conceptually mappings between names and values. Both * mechanisms can be used to pass user-defined information to a * Java process. Environment variables have a more global effect, * because they are visible to all descendants of the process * which defines them, not just the immediate Java subprocess. * They can have subtly different semantics, such as case * insensitivity, on different operating systems. For these * reasons, environment variables are more likely to have * unintended side effects. It is best to use system properties * where possible. Environment variables should be used when a * global effect is desired, or when an external system interface * requires an environment variable (such as {@code PATH}). * *

On UNIX systems the alphabetic case of {@code name} is * typically significant, while on Microsoft Windows systems it is * typically not. For example, the expression * {@code System.getenv("FOO").equals(System.getenv("foo"))} * is likely to be true on Microsoft Windows. * * @param name the name of the environment variable * @return the string value of the variable, or {@code null} * if the variable is not defined in the system environment * @throws NullPointerException if {@code name} is {@code null} * @see #getenv() * @see ProcessBuilder#environment() */ public static String getenv(String name) { return ProcessEnvironment.getenv(name); } /** * Returns an unmodifiable string map view of the current system environment. * The environment is a system-dependent mapping from names to * values which is passed from parent to child processes. * *

If the system does not support environment variables, an * empty map is returned. * *

The returned map will never contain null keys or values. * Attempting to query the presence of a null key or value will * throw a {@link NullPointerException}. Attempting to query * the presence of a key or value which is not of type * {@link String} will throw a {@link ClassCastException}. * *

The returned map and its collection views may not obey the * general contract of the {@link Object#equals} and * {@link Object#hashCode} methods. * *

The returned map is typically case-sensitive on all platforms. * *

When passing information to a Java subprocess, * system properties * are generally preferred over environment variables. * * @return the environment as a map of variable names to values * @see #getenv(String) * @see ProcessBuilder#environment() * @since 1.5 */ public static java.util.Map getenv() { return ProcessEnvironment.getenv(); } /** * {@code System.Logger} instances log messages that will be * routed to the underlying logging framework the {@link System.LoggerFinder * LoggerFinder} uses. * * {@code System.Logger} instances are typically obtained from * the {@link java.lang.System System} class, by calling * {@link java.lang.System#getLogger(java.lang.String) System.getLogger(loggerName)} * or {@link java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle) * System.getLogger(loggerName, bundle)}. * * @see java.lang.System#getLogger(java.lang.String) * @see java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle) * @see java.lang.System.LoggerFinder * * @since 9 */ public interface Logger { /** * System {@linkplain Logger loggers} levels. * * A level has a {@linkplain #getName() name} and {@linkplain * #getSeverity() severity}. * Level values are {@link #ALL}, {@link #TRACE}, {@link #DEBUG}, * {@link #INFO}, {@link #WARNING}, {@link #ERROR}, {@link #OFF}, * by order of increasing severity. *
* {@link #ALL} and {@link #OFF} * are simple markers with severities mapped respectively to * {@link java.lang.Integer#MIN_VALUE Integer.MIN_VALUE} and * {@link java.lang.Integer#MAX_VALUE Integer.MAX_VALUE}. *

* Severity values and Mapping to {@code java.util.logging.Level}. *

* {@linkplain System.Logger.Level System logger levels} are mapped to * {@linkplain java.logging/java.util.logging.Level java.util.logging levels} * of corresponding severity. *
The mapping is as follows: *

* * * * * * * * * * * * * * * * * * * * * * *
System.Logger Severity Level Mapping
System.Logger Levelsjava.util.logging Levels
{@link Logger.Level#ALL ALL}{@link java.logging/java.util.logging.Level#ALL ALL}
{@link Logger.Level#TRACE TRACE}{@link java.logging/java.util.logging.Level#FINER FINER}
{@link Logger.Level#DEBUG DEBUG}{@link java.logging/java.util.logging.Level#FINE FINE}
{@link Logger.Level#INFO INFO}{@link java.logging/java.util.logging.Level#INFO INFO}
{@link Logger.Level#WARNING WARNING}{@link java.logging/java.util.logging.Level#WARNING WARNING}
{@link Logger.Level#ERROR ERROR}{@link java.logging/java.util.logging.Level#SEVERE SEVERE}
{@link Logger.Level#OFF OFF}{@link java.logging/java.util.logging.Level#OFF OFF}
* * @since 9 * * @see java.lang.System.LoggerFinder * @see java.lang.System.Logger */ @SuppressWarnings("doclint:reference") // cross-module links public enum Level { // for convenience, we're reusing java.util.logging.Level int values // the mapping logic in sun.util.logging.PlatformLogger depends // on this. /** * A marker to indicate that all levels are enabled. * This level {@linkplain #getSeverity() severity} is * {@link Integer#MIN_VALUE}. */ ALL(Integer.MIN_VALUE), // typically mapped to/from j.u.l.Level.ALL /** * {@code TRACE} level: usually used to log diagnostic information. * This level {@linkplain #getSeverity() severity} is * {@code 400}. */ TRACE(400), // typically mapped to/from j.u.l.Level.FINER /** * {@code DEBUG} level: usually used to log debug information traces. * This level {@linkplain #getSeverity() severity} is * {@code 500}. */ DEBUG(500), // typically mapped to/from j.u.l.Level.FINEST/FINE/CONFIG /** * {@code INFO} level: usually used to log information messages. * This level {@linkplain #getSeverity() severity} is * {@code 800}. */ INFO(800), // typically mapped to/from j.u.l.Level.INFO /** * {@code WARNING} level: usually used to log warning messages. * This level {@linkplain #getSeverity() severity} is * {@code 900}. */ WARNING(900), // typically mapped to/from j.u.l.Level.WARNING /** * {@code ERROR} level: usually used to log error messages. * This level {@linkplain #getSeverity() severity} is * {@code 1000}. */ ERROR(1000), // typically mapped to/from j.u.l.Level.SEVERE /** * A marker to indicate that all levels are disabled. * This level {@linkplain #getSeverity() severity} is * {@link Integer#MAX_VALUE}. */ OFF(Integer.MAX_VALUE); // typically mapped to/from j.u.l.Level.OFF private final int severity; private Level(int severity) { this.severity = severity; } /** * Returns the name of this level. * @return this level {@linkplain #name()}. */ public final String getName() { return name(); } /** * Returns the severity of this level. * A higher severity means a more severe condition. * @return this level severity. */ public final int getSeverity() { return severity; } } /** * Returns the name of this logger. * * @return the logger name. */ public String getName(); /** * Checks if a message of the given level would be logged by * this logger. * * @param level the log message level. * @return {@code true} if the given log message level is currently * being logged. * * @throws NullPointerException if {@code level} is {@code null}. */ public boolean isLoggable(Level level); /** * Logs a message. * * @implSpec The default implementation for this method calls * {@code this.log(level, (ResourceBundle)null, msg, (Object[])null);} * * @param level the log message level. * @param msg the string message (or a key in the message catalog, if * this logger is a {@link * LoggerFinder#getLocalizedLogger(java.lang.String, * java.util.ResourceBundle, java.lang.Module) localized logger}); * can be {@code null}. * * @throws NullPointerException if {@code level} is {@code null}. */ public default void log(Level level, String msg) { log(level, (ResourceBundle) null, msg, (Object[]) null); } /** * Logs a lazily supplied message. * * If the logger is currently enabled for the given log message level * then a message is logged that is the result produced by the * given supplier function. Otherwise, the supplier is not operated on. * * @implSpec When logging is enabled for the given level, the default * implementation for this method calls * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), (Object[])null);} * * @param level the log message level. * @param msgSupplier a supplier function that produces a message. * * @throws NullPointerException if {@code level} is {@code null}, * or {@code msgSupplier} is {@code null}. */ public default void log(Level level, Supplier msgSupplier) { Objects.requireNonNull(msgSupplier); if (isLoggable(Objects.requireNonNull(level))) { log(level, (ResourceBundle) null, msgSupplier.get(), (Object[]) null); } } /** * Logs a message produced from the given object. * * If the logger is currently enabled for the given log message level then * a message is logged that, by default, is the result produced from * calling toString on the given object. * Otherwise, the object is not operated on. * * @implSpec When logging is enabled for the given level, the default * implementation for this method calls * {@code this.log(level, (ResourceBundle)null, obj.toString(), (Object[])null);} * * @param level the log message level. * @param obj the object to log. * * @throws NullPointerException if {@code level} is {@code null}, or * {@code obj} is {@code null}. */ public default void log(Level level, Object obj) { Objects.requireNonNull(obj); if (isLoggable(Objects.requireNonNull(level))) { this.log(level, (ResourceBundle) null, obj.toString(), (Object[]) null); } } /** * Logs a message associated with a given throwable. * * @implSpec The default implementation for this method calls * {@code this.log(level, (ResourceBundle)null, msg, thrown);} * * @param level the log message level. * @param msg the string message (or a key in the message catalog, if * this logger is a {@link * LoggerFinder#getLocalizedLogger(java.lang.String, * java.util.ResourceBundle, java.lang.Module) localized logger}); * can be {@code null}. * @param thrown a {@code Throwable} associated with the log message; * can be {@code null}. * * @throws NullPointerException if {@code level} is {@code null}. */ public default void log(Level level, String msg, Throwable thrown) { this.log(level, null, msg, thrown); } /** * Logs a lazily supplied message associated with a given throwable. * * If the logger is currently enabled for the given log message level * then a message is logged that is the result produced by the * given supplier function. Otherwise, the supplier is not operated on. * * @implSpec When logging is enabled for the given level, the default * implementation for this method calls * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), thrown);} * * @param level one of the log message level identifiers. * @param msgSupplier a supplier function that produces a message. * @param thrown a {@code Throwable} associated with log message; * can be {@code null}. * * @throws NullPointerException if {@code level} is {@code null}, or * {@code msgSupplier} is {@code null}. */ public default void log(Level level, Supplier msgSupplier, Throwable thrown) { Objects.requireNonNull(msgSupplier); if (isLoggable(Objects.requireNonNull(level))) { this.log(level, null, msgSupplier.get(), thrown); } } /** * Logs a message with an optional list of parameters. * * @implSpec The default implementation for this method calls * {@code this.log(level, (ResourceBundle)null, format, params);} * * @param level one of the log message level identifiers. * @param format the string message format in {@link * java.text.MessageFormat} format, (or a key in the message * catalog, if this logger is a {@link * LoggerFinder#getLocalizedLogger(java.lang.String, * java.util.ResourceBundle, java.lang.Module) localized logger}); * can be {@code null}. * @param params an optional list of parameters to the message (may be * none). * * @throws NullPointerException if {@code level} is {@code null}. */ public default void log(Level level, String format, Object... params) { this.log(level, null, format, params); } /** * Logs a localized message associated with a given throwable. * * If the given resource bundle is non-{@code null}, the {@code msg} * string is localized using the given resource bundle. * Otherwise the {@code msg} string is not localized. * * @param level the log message level. * @param bundle a resource bundle to localize {@code msg}; can be * {@code null}. * @param msg the string message (or a key in the message catalog, * if {@code bundle} is not {@code null}); can be {@code null}. * @param thrown a {@code Throwable} associated with the log message; * can be {@code null}. * * @throws NullPointerException if {@code level} is {@code null}. */ public void log(Level level, ResourceBundle bundle, String msg, Throwable thrown); /** * Logs a message with resource bundle and an optional list of * parameters. * * If the given resource bundle is non-{@code null}, the {@code format} * string is localized using the given resource bundle. * Otherwise the {@code format} string is not localized. * * @param level the log message level. * @param bundle a resource bundle to localize {@code format}; can be * {@code null}. * @param format the string message format in {@link * java.text.MessageFormat} format, (or a key in the message * catalog if {@code bundle} is not {@code null}); can be {@code null}. * @param params an optional list of parameters to the message (may be * none). * * @throws NullPointerException if {@code level} is {@code null}. */ public void log(Level level, ResourceBundle bundle, String format, Object... params); } /** * The {@code LoggerFinder} service is responsible for creating, managing, * and configuring loggers to the underlying framework it uses. * * A logger finder is a concrete implementation of this class that has a * zero-argument constructor and implements the abstract methods defined * by this class. * The loggers returned from a logger finder are capable of routing log * messages to the logging backend this provider supports. * A given invocation of the Java Runtime maintains a single * system-wide LoggerFinder instance that is loaded as follows: *

*

* An application can replace the logging backend * even when the java.logging module is present, by simply providing * and declaring an implementation of the {@link LoggerFinder} service. *

* Default Implementation *

* The system default {@code LoggerFinder} implementation uses * {@code java.util.logging} as the backend framework when the * {@code java.logging} module is present. * It returns a {@linkplain System.Logger logger} instance * that will route log messages to a {@link java.logging/java.util.logging.Logger * java.util.logging.Logger}. Otherwise, if {@code java.logging} is not * present, the default implementation will return a simple logger * instance that will route log messages of {@code INFO} level and above to * the console ({@code System.err}). *

* Logging Configuration *

* {@linkplain Logger Logger} instances obtained from the * {@code LoggerFinder} factory methods are not directly configurable by * the application. Configuration is the responsibility of the underlying * logging backend, and usually requires using APIs specific to that backend. *

For the default {@code LoggerFinder} implementation * using {@code java.util.logging} as its backend, refer to * {@link java.logging/java.util.logging java.util.logging} for logging configuration. * For the default {@code LoggerFinder} implementation returning simple loggers * when the {@code java.logging} module is absent, the configuration * is implementation dependent. *

* Usually an application that uses a logging framework will log messages * through a logger facade defined (or supported) by that framework. * Applications that wish to use an external framework should log * through the facade associated with that framework. *

* A system class that needs to log messages will typically obtain * a {@link System.Logger} instance to route messages to the logging * framework selected by the application. *

* Libraries and classes that only need loggers to produce log messages * should not attempt to configure loggers by themselves, as that * would make them dependent from a specific implementation of the * {@code LoggerFinder} service. *

* Message Levels and Mapping to backend levels *

* A logger finder is responsible for mapping from a {@code * System.Logger.Level} to a level supported by the logging backend it uses. *
The default LoggerFinder using {@code java.util.logging} as the backend * maps {@code System.Logger} levels to * {@linkplain java.logging/java.util.logging.Level java.util.logging} levels * of corresponding severity - as described in {@link Logger.Level * Logger.Level}. * * @see java.lang.System * @see java.lang.System.Logger * * @since 9 */ @SuppressWarnings("doclint:reference") // cross-module links public abstract static class LoggerFinder { /** * Creates a new instance of {@code LoggerFinder}. * * @implNote It is recommended that a {@code LoggerFinder} service * implementation does not perform any heavy initialization in its * constructor, in order to avoid possible risks of deadlock or class * loading cycles during the instantiation of the service provider. */ protected LoggerFinder() { } /** * Returns an instance of {@link Logger Logger} * for the given {@code module}. * * @param name the name of the logger. * @param module the module for which the logger is being requested. * * @return a {@link Logger logger} suitable for use within the given * module. * @throws NullPointerException if {@code name} is {@code null} or * {@code module} is {@code null}. */ public abstract Logger getLogger(String name, Module module); /** * Returns a localizable instance of {@link Logger Logger} * for the given {@code module}. * The returned logger will use the provided resource bundle for * message localization. * * @implSpec By default, this method calls {@link * #getLogger(java.lang.String, java.lang.Module) * this.getLogger(name, module)} to obtain a logger, then wraps that * logger in a {@link Logger} instance where all methods that do not * take a {@link ResourceBundle} as parameter are redirected to one * which does - passing the given {@code bundle} for * localization. So for instance, a call to {@link * Logger#log(Logger.Level, String) Logger.log(Level.INFO, msg)} * will end up as a call to {@link * Logger#log(Logger.Level, ResourceBundle, String, Object...) * Logger.log(Level.INFO, bundle, msg, (Object[])null)} on the wrapped * logger instance. * Note however that by default, string messages returned by {@link * java.util.function.Supplier Supplier<String>} will not be * localized, as it is assumed that such strings are messages which are * already constructed, rather than keys in a resource bundle. *

* An implementation of {@code LoggerFinder} may override this method, * for example, when the underlying logging backend provides its own * mechanism for localizing log messages, then such a * {@code LoggerFinder} would be free to return a logger * that makes direct use of the mechanism provided by the backend. * * @param name the name of the logger. * @param bundle a resource bundle; can be {@code null}. * @param module the module for which the logger is being requested. * @return an instance of {@link Logger Logger} which will use the * provided resource bundle for message localization. * * @throws NullPointerException if {@code name} is {@code null} or * {@code module} is {@code null}. */ public Logger getLocalizedLogger(String name, ResourceBundle bundle, Module module) { return new LocalizedLoggerWrapper<>(getLogger(name, module), bundle); } /** * Returns the {@code LoggerFinder} instance. There is one * single system-wide {@code LoggerFinder} instance in * the Java Runtime. See the class specification of how the * {@link LoggerFinder LoggerFinder} implementation is located and * loaded. * * @return the {@link LoggerFinder LoggerFinder} instance. */ public static LoggerFinder getLoggerFinder() { return accessProvider(); } private static volatile LoggerFinder service; static LoggerFinder accessProvider() { // We do not need to synchronize: LoggerFinderLoader will // always return the same instance, so if we don't have it, // just fetch it again. LoggerFinder finder = service; if (finder == null) { finder = LoggerFinderLoader.getLoggerFinder(); if (finder instanceof TemporaryLoggerFinder) return finder; service = finder; } return finder; } } /** * Returns an instance of {@link Logger Logger} for the caller's * use. * * @implSpec * Instances returned by this method route messages to loggers * obtained by calling {@link LoggerFinder#getLogger(java.lang.String, * java.lang.Module) LoggerFinder.getLogger(name, module)}, where * {@code module} is the caller's module. * In cases where {@code System.getLogger} is called from a context where * there is no caller frame on the stack (e.g when called directly * from a JNI attached thread), {@code IllegalCallerException} is thrown. * To obtain a logger in such a context, use an auxiliary class that will * implicitly be identified as the caller, or use the system {@link * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead. * Note that doing the latter may eagerly initialize the underlying * logging system. * * @apiNote * This method may defer calling the {@link * LoggerFinder#getLogger(java.lang.String, java.lang.Module) * LoggerFinder.getLogger} method to create an actual logger supplied by * the logging backend, for instance, to allow loggers to be obtained during * the system initialization time. * * @param name the name of the logger. * @return an instance of {@link Logger} that can be used by the calling * class. * @throws NullPointerException if {@code name} is {@code null}. * @throws IllegalCallerException if there is no Java caller frame on the * stack. * * @since 9 */ @CallerSensitive public static Logger getLogger(String name) { Objects.requireNonNull(name); final Class caller = Reflection.getCallerClass(); if (caller == null) { throw new IllegalCallerException("no caller frame"); } return LazyLoggers.getLogger(name, caller.getModule()); } /** * Returns a localizable instance of {@link Logger * Logger} for the caller's use. * The returned logger will use the provided resource bundle for message * localization. * * @implSpec * The returned logger will perform message localization as specified * by {@link LoggerFinder#getLocalizedLogger(java.lang.String, * java.util.ResourceBundle, java.lang.Module) * LoggerFinder.getLocalizedLogger(name, bundle, module)}, where * {@code module} is the caller's module. * In cases where {@code System.getLogger} is called from a context where * there is no caller frame on the stack (e.g when called directly * from a JNI attached thread), {@code IllegalCallerException} is thrown. * To obtain a logger in such a context, use an auxiliary class that * will implicitly be identified as the caller, or use the system {@link * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead. * Note that doing the latter may eagerly initialize the underlying * logging system. * * @apiNote * This method is intended to be used after the system is fully initialized. * This method may trigger the immediate loading and initialization * of the {@link LoggerFinder} service, which may cause issues if the * Java Runtime is not ready to initialize the concrete service * implementation yet. * System classes which may be loaded early in the boot sequence and * need to log localized messages should create a logger using * {@link #getLogger(java.lang.String)} and then use the log methods that * take a resource bundle as parameter. * * @param name the name of the logger. * @param bundle a resource bundle. * @return an instance of {@link Logger} which will use the provided * resource bundle for message localization. * @throws NullPointerException if {@code name} is {@code null} or * {@code bundle} is {@code null}. * @throws IllegalCallerException if there is no Java caller frame on the * stack. * * @since 9 */ @CallerSensitive public static Logger getLogger(String name, ResourceBundle bundle) { final ResourceBundle rb = Objects.requireNonNull(bundle); Objects.requireNonNull(name); final Class caller = Reflection.getCallerClass(); if (caller == null) { throw new IllegalCallerException("no caller frame"); } return LoggerFinder.accessProvider() .getLocalizedLogger(name, rb, caller.getModule()); } /** * Initiates the {@linkplain Runtime##shutdown shutdown sequence} of the Java Virtual * Machine. This method initiates the shutdown sequence (if it is not already initiated) * and then blocks indefinitely. This method neither returns nor throws an exception; * that is, it does not complete either normally or abruptly. *

* The argument serves as a status code. By convention, a nonzero status code * indicates abnormal termination. *

* The call {@code System.exit(n)} is effectively equivalent to the call: * {@snippet : * Runtime.getRuntime().exit(n) * } * * @implNote * The initiation of the shutdown sequence is logged by {@link Runtime#exit(int)}. * * @param status exit status. * @see java.lang.Runtime#exit(int) */ public static void exit(int status) { Runtime.getRuntime().exit(status); } /** * Runs the garbage collector in the Java Virtual Machine. *

* Calling the {@code gc} method suggests that the Java Virtual Machine * expend effort toward recycling unused objects in order to * make the memory they currently occupy available for reuse * by the Java Virtual Machine. * When control returns from the method call, the Java Virtual Machine * has made a best effort to reclaim space from all unused objects. * There is no guarantee that this effort will recycle any particular * number of unused objects, reclaim any particular amount of space, or * complete at any particular time, if at all, before the method returns or ever. * There is also no guarantee that this effort will determine * the change of reachability in any particular number of objects, * or that any particular number of {@link java.lang.ref.Reference Reference} * objects will be cleared and enqueued. * *

* The call {@code System.gc()} is effectively equivalent to the * call: * 

     * Runtime.getRuntime().gc()
     *
* * @see java.lang.Runtime#gc() */ public static void gc() { Runtime.getRuntime().gc(); } /** * Runs the finalization methods of any objects pending finalization. * * Calling this method suggests that the Java Virtual Machine expend * effort toward running the {@code finalize} methods of objects * that have been found to be discarded but whose {@code finalize} * methods have not yet been run. When control returns from the * method call, the Java Virtual Machine has made a best effort to * complete all outstanding finalizations. *

* The call {@code System.runFinalization()} is effectively * equivalent to the call: * 

     * Runtime.getRuntime().runFinalization()
     *
* * @deprecated Finalization has been deprecated for removal. See * {@link java.lang.Object#finalize} for background information and details * about migration options. *

* When running in a JVM in which finalization has been disabled or removed, * no objects will be pending finalization, so this method does nothing. * * @see java.lang.Runtime#runFinalization() * @jls 12.6 Finalization of Class Instances */ @Deprecated(since="18", forRemoval=true) @SuppressWarnings("removal") public static void runFinalization() { Runtime.getRuntime().runFinalization(); } /** * Loads the native library specified by the filename argument. The filename * argument must be an absolute path name. * * If the filename argument, when stripped of any platform-specific library * prefix, path, and file extension, indicates a library whose name is, * for example, L, and a native library called L is statically linked * with the VM, then the JNI_OnLoad_L function exported by the library * is invoked rather than attempting to load a dynamic library. * A filename matching the argument does not have to exist in the * file system. * See the JNI Specification * for more details. * * Otherwise, the filename argument is mapped to a native library image in * an implementation-dependent manner. * *

* The call {@code System.load(name)} is effectively equivalent * to the call: * 

     * Runtime.getRuntime().load(name)
     *
* * @param filename the file to load. * @throws UnsatisfiedLinkError if either the filename is not an * absolute path name, the native library is not statically * linked with the VM, or the library cannot be mapped to * a native library image by the host system. * @throws NullPointerException if {@code filename} is {@code null} * @throws IllegalCallerException if the caller is in a module that * does not have native access enabled. * * @spec jni/index.html Java Native Interface Specification * @see java.lang.Runtime#load(java.lang.String) */ @CallerSensitive @Restricted public static void load(String filename) { Class caller = Reflection.getCallerClass(); Reflection.ensureNativeAccess(caller, System.class, "load", false); Runtime.getRuntime().load0(caller, filename); } /** * Loads the native library specified by the {@code libname} * argument. The {@code libname} argument must not contain any platform * specific prefix, file extension or path. If a native library * called {@code libname} is statically linked with the VM, then the * JNI_OnLoad_{@code libname} function exported by the library is invoked. * See the JNI Specification * for more details. * * Otherwise, the libname argument is loaded from a system library * location and mapped to a native library image in an * implementation-dependent manner. *

* The call {@code System.loadLibrary(name)} is effectively * equivalent to the call * 

     * Runtime.getRuntime().loadLibrary(name)
     *
* * @param libname the name of the library. * @throws UnsatisfiedLinkError if either the libname argument * contains a file path, the native library is not statically * linked with the VM, or the library cannot be mapped to a * native library image by the host system. * @throws NullPointerException if {@code libname} is {@code null} * @throws IllegalCallerException if the caller is in a module that * does not have native access enabled. * * @spec jni/index.html Java Native Interface Specification * @see java.lang.Runtime#loadLibrary(java.lang.String) */ @CallerSensitive @Restricted public static void loadLibrary(String libname) { Class caller = Reflection.getCallerClass(); Reflection.ensureNativeAccess(caller, System.class, "loadLibrary", false); Runtime.getRuntime().loadLibrary0(caller, libname); } /** * Maps a library name into a platform-specific string representing * a native library. * * @param libname the name of the library. * @return a platform-dependent native library name. * @throws NullPointerException if {@code libname} is {@code null} * @see java.lang.System#loadLibrary(java.lang.String) * @see java.lang.ClassLoader#findLibrary(java.lang.String) * @since 1.2 */ public static native String mapLibraryName(String libname); /** * Create PrintStream for stdout/err based on encoding. */ private static PrintStream newPrintStream(OutputStream out, String enc) { if (enc != null) { return new PrintStream(new BufferedOutputStream(out, 128), true, Charset.forName(enc, UTF_8.INSTANCE)); } return new PrintStream(new BufferedOutputStream(out, 128), true); } /** * Logs an exception/error at initialization time to stdout or stderr. * * @param printToStderr to print to stderr rather than stdout * @param printStackTrace to print the stack trace * @param msg the message to print before the exception, can be {@code null} * @param e the exception or error */ private static void logInitException(boolean printToStderr, boolean printStackTrace, String msg, Throwable e) { if (VM.initLevel() < 1) { throw new InternalError("system classes not initialized"); } PrintStream log = (printToStderr) ? err : out; if (msg != null) { log.println(msg); } if (printStackTrace) { e.printStackTrace(log); } else { log.println(e); for (Throwable suppressed : e.getSuppressed()) { log.println("Suppressed: " + suppressed); } Throwable cause = e.getCause(); if (cause != null) { log.println("Caused by: " + cause); } } } /** * Create the Properties object from a map - masking out system properties * that are not intended for public access. */ private static Properties createProperties(Map initialProps) { Properties properties = new Properties(initialProps.size()); for (var entry : initialProps.entrySet()) { String prop = entry.getKey(); switch (prop) { // Do not add private system properties to the Properties case "sun.nio.MaxDirectMemorySize": case "sun.nio.PageAlignDirectMemory": // used by java.lang.Integer.IntegerCache case "java.lang.Integer.IntegerCache.high": // used by sun.launcher.LauncherHelper case "sun.java.launcher.diag": // used by jdk.internal.loader.ClassLoaders case "jdk.boot.class.path.append": break; default: properties.put(prop, entry.getValue()); } } return properties; } /** * Initialize the system class. Called after thread initialization. */ private static void initPhase1() { // register the shared secrets - do this first, since SystemProps.initProperties // might initialize CharsetDecoders that rely on it setJavaLangAccess(); // VM might invoke JNU_NewStringPlatform() to set those encoding // sensitive properties (user.home, user.name, boot.class.path, etc.) // during "props" initialization. // The charset is initialized in System.c and does not depend on the Properties. Map tempProps = SystemProps.initProperties(); VersionProps.init(tempProps); // There are certain system configurations that may be controlled by // VM options such as the maximum amount of direct memory and // Integer cache size used to support the object identity semantics // of autoboxing. Typically, the library will obtain these values // from the properties set by the VM. If the properties are for // internal implementation use only, these properties should be // masked from the system properties. // // Save a private copy of the system properties object that // can only be accessed by the internal implementation. VM.saveProperties(tempProps); props = createProperties(tempProps); // Check if sun.jnu.encoding is supported. If not, replace it with UTF-8. var jnuEncoding = props.getProperty("sun.jnu.encoding"); if (jnuEncoding == null || !Charset.isSupported(jnuEncoding)) { notSupportedJnuEncoding = jnuEncoding == null ? "null" : jnuEncoding; props.setProperty("sun.jnu.encoding", "UTF-8"); } StaticProperty.javaHome(); // Load StaticProperty to cache the property values lineSeparator = props.getProperty("line.separator"); FileInputStream fdIn = new In(FileDescriptor.in); FileOutputStream fdOut = new Out(FileDescriptor.out); FileOutputStream fdErr = new Out(FileDescriptor.err); initialIn = new BufferedInputStream(fdIn); setIn0(initialIn); // stdout/err.encoding are set when the VM is associated with the terminal, // thus they are equivalent to Console.charset(), otherwise the encodings // of those properties default to native.encoding setOut0(newPrintStream(fdOut, props.getProperty("stdout.encoding"))); initialErr = newPrintStream(fdErr, props.getProperty("stderr.encoding")); setErr0(initialErr); // Setup Java signal handlers for HUP, TERM, and INT (where available). Terminator.setup(); // Initialize any miscellaneous operating system settings that need to be // set for the class libraries. Currently this is no-op everywhere except // for Windows where the process-wide error mode is set before the java.io // classes are used. VM.initializeOSEnvironment(); // start Finalizer and Reference Handler threads SharedSecrets.getJavaLangRefAccess().startThreads(); // system properties, java.lang and other core classes are now initialized VM.initLevel(1); } /** * System.in. */ private static class In extends FileInputStream { In(FileDescriptor fd) { super(fd); } @Override public int read() throws IOException { boolean attempted = Blocker.begin(); try { return super.read(); } finally { Blocker.end(attempted); } } @Override public int read(byte[] b) throws IOException { boolean attempted = Blocker.begin(); try { return super.read(b); } finally { Blocker.end(attempted); } } @Override public int read(byte[] b, int off, int len) throws IOException { boolean attempted = Blocker.begin(); try { return super.read(b, off, len); } finally { Blocker.end(attempted); } } } /** * System.out/System.err wrap this output stream. */ private static class Out extends FileOutputStream { Out(FileDescriptor fd) { super(fd); } @Override public void write(int b) throws IOException { boolean attempted = Blocker.begin(); try { super.write(b); } finally { Blocker.end(attempted); } } @Override public void write(byte[] b) throws IOException { boolean attempted = Blocker.begin(); try { super.write(b); } finally { Blocker.end(attempted); } } @Override public void write(byte[] b, int off, int len) throws IOException { boolean attempted = Blocker.begin(); try { super.write(b, off, len); } finally { Blocker.end(attempted); } } } // @see #initPhase2() static ModuleLayer bootLayer; /* * Invoked by VM. Phase 2 module system initialization. * Only classes in java.base can be loaded in this phase. * * @param printToStderr print exceptions to stderr rather than stdout * @param printStackTrace print stack trace when exception occurs * * @return JNI_OK for success, JNI_ERR for failure */ private static int initPhase2(boolean printToStderr, boolean printStackTrace) { try { bootLayer = ModuleBootstrap.boot(); } catch (Exception | Error e) { logInitException(printToStderr, printStackTrace, "Error occurred during initialization of boot layer", e); return -1; // JNI_ERR } // module system initialized VM.initLevel(2); return 0; // JNI_OK } /* * Invoked by VM. Phase 3 is the final system initialization: * 1. set system class loader * 2. set TCCL * * This method must be called after the module system initialization. */ private static void initPhase3() { // Emit a warning if java.io.tmpdir is set via the command line // to a directory that doesn't exist if (SystemProps.isBadIoTmpdir()) { System.err.println("WARNING: java.io.tmpdir directory does not exist"); } String smProp = System.getProperty("java.security.manager"); if (smProp != null) { switch (smProp) { case "disallow": break; case "allow": case "": case "default": default: throw new Error("A command line option has attempted to allow or enable the Security Manager." + " Enabling a Security Manager is not supported."); } } // Emit a warning if `sun.jnu.encoding` is not supported. if (notSupportedJnuEncoding != null) { System.err.println( "WARNING: The encoding of the underlying platform's" + " file system is not supported: " + notSupportedJnuEncoding); } // initializing the system class loader VM.initLevel(3); // system class loader initialized ClassLoader scl = ClassLoader.initSystemClassLoader(); // set TCCL Thread.currentThread().setContextClassLoader(scl); // system is fully initialized VM.initLevel(4); } private static void setJavaLangAccess() { // Allow privileged classes outside of java.lang SharedSecrets.setJavaLangAccess(new JavaLangAccess() { public List getDeclaredPublicMethods(Class klass, String name, Class... parameterTypes) { return klass.getDeclaredPublicMethods(name, parameterTypes); } public Method findMethod(Class klass, boolean publicOnly, String name, Class... parameterTypes) { return klass.findMethod(publicOnly, name, parameterTypes); } public jdk.internal.reflect.ConstantPool getConstantPool(Class klass) { return klass.getConstantPool(); } public boolean casAnnotationType(Class klass, AnnotationType oldType, AnnotationType newType) { return klass.casAnnotationType(oldType, newType); } public AnnotationType getAnnotationType(Class klass) { return klass.getAnnotationType(); } public Map, Annotation> getDeclaredAnnotationMap(Class klass) { return klass.getDeclaredAnnotationMap(); } public byte[] getRawClassAnnotations(Class klass) { return klass.getRawAnnotations(); } public byte[] getRawClassTypeAnnotations(Class klass) { return klass.getRawTypeAnnotations(); } public byte[] getRawExecutableTypeAnnotations(Executable executable) { return Class.getExecutableTypeAnnotationBytes(executable); } public > E[] getEnumConstantsShared(Class klass) { return klass.getEnumConstantsShared(); } public int classFileVersion(Class clazz) { return clazz.getClassFileVersion(); } public void blockedOn(Interruptible b) { Thread.currentThread().blockedOn(b); } public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) { Shutdown.add(slot, registerShutdownInProgress, hook); } @SuppressWarnings("removal") public void invokeFinalize(Object o) throws Throwable { o.finalize(); } public ConcurrentHashMap createOrGetClassLoaderValueMap(ClassLoader cl) { return cl.createOrGetClassLoaderValueMap(); } public Class defineClass(ClassLoader loader, String name, byte[] b, ProtectionDomain pd, String source) { return ClassLoader.defineClass1(loader, name, b, 0, b.length, pd, source); } public Class defineClass(ClassLoader loader, Class lookup, String name, byte[] b, ProtectionDomain pd, boolean initialize, int flags, Object classData) { return ClassLoader.defineClass0(loader, lookup, name, b, 0, b.length, pd, initialize, flags, classData); } public Class findBootstrapClassOrNull(String name) { return ClassLoader.findBootstrapClassOrNull(name); } public Package definePackage(ClassLoader cl, String name, Module module) { return cl.definePackage(name, module); } public Module defineModule(ClassLoader loader, ModuleDescriptor descriptor, URI uri) { return new Module(null, loader, descriptor, uri); } public Module defineUnnamedModule(ClassLoader loader) { return new Module(loader); } public void addReads(Module m1, Module m2) { m1.implAddReads(m2); } public void addReadsAllUnnamed(Module m) { m.implAddReadsAllUnnamed(); } public void addExports(Module m, String pn) { m.implAddExports(pn); } public void addExports(Module m, String pn, Module other) { m.implAddExports(pn, other); } public void addExportsToAllUnnamed(Module m, String pn) { m.implAddExportsToAllUnnamed(pn); } public void addOpens(Module m, String pn, Module other) { m.implAddOpens(pn, other); } public void addOpensToAllUnnamed(Module m, String pn) { m.implAddOpensToAllUnnamed(pn); } public void addUses(Module m, Class service) { m.implAddUses(service); } public boolean isReflectivelyExported(Module m, String pn, Module other) { return m.isReflectivelyExported(pn, other); } public boolean isReflectivelyOpened(Module m, String pn, Module other) { return m.isReflectivelyOpened(pn, other); } public Module addEnableNativeAccess(Module m) { return m.implAddEnableNativeAccess(); } public boolean addEnableNativeAccess(ModuleLayer layer, String name) { return layer.addEnableNativeAccess(name); } public void addEnableNativeAccessToAllUnnamed() { Module.implAddEnableNativeAccessToAllUnnamed(); } public void ensureNativeAccess(Module m, Class owner, String methodName, Class currentClass, boolean jni) { m.ensureNativeAccess(owner, methodName, currentClass, jni); } public ServicesCatalog getServicesCatalog(ModuleLayer layer) { return layer.getServicesCatalog(); } public void bindToLoader(ModuleLayer layer, ClassLoader loader) { layer.bindToLoader(loader); } public Stream layers(ModuleLayer layer) { return layer.layers(); } public Stream layers(ClassLoader loader) { return ModuleLayer.layers(loader); } public int countPositives(byte[] bytes, int offset, int length) { return StringCoding.countPositives(bytes, offset, length); } public int countNonZeroAscii(String s) { return StringCoding.countNonZeroAscii(s); } public String uncheckedNewStringNoRepl(byte[] bytes, Charset cs) throws CharacterCodingException { return String.newStringNoRepl(bytes, cs); } public char uncheckedGetUTF16Char(byte[] bytes, int index) { return StringUTF16.getChar(bytes, index); } public void uncheckedPutCharUTF16(byte[] bytes, int index, int ch) { StringUTF16.putChar(bytes, index, ch); } public byte[] uncheckedGetBytesNoRepl(String s, Charset cs) throws CharacterCodingException { return String.getBytesNoRepl(s, cs); } public String newStringUTF8NoRepl(byte[] bytes, int off, int len) { return String.newStringUTF8NoRepl(bytes, off, len, true); } public byte[] getBytesUTF8NoRepl(String s) { return String.getBytesUTF8NoRepl(s); } public void inflateBytesToChars(byte[] src, int srcOff, char[] dst, int dstOff, int len) { StringLatin1.inflate(src, srcOff, dst, dstOff, len); } public int decodeASCII(byte[] src, int srcOff, char[] dst, int dstOff, int len) { return String.decodeASCII(src, srcOff, dst, dstOff, len); } public int uncheckedEncodeASCII(char[] src, int srcOff, byte[] dst, int dstOff, int len) { return StringCoding.implEncodeAsciiArray(src, srcOff, dst, dstOff, len); } public InputStream initialSystemIn() { return initialIn; } public PrintStream initialSystemErr() { return initialErr; } public void setCause(Throwable t, Throwable cause) { t.setCause(cause); } public ProtectionDomain protectionDomain(Class c) { return c.getProtectionDomain(); } public MethodHandle stringConcatHelper(String name, MethodType methodType) { return StringConcatHelper.lookupStatic(name, methodType); } public long stringConcatInitialCoder() { return StringConcatHelper.initialCoder(); } public long stringConcatMix(long lengthCoder, String constant) { return StringConcatHelper.mix(lengthCoder, constant); } public long stringConcatMix(long lengthCoder, char value) { return StringConcatHelper.mix(lengthCoder, value); } public Object uncheckedStringConcat1(String[] constants) { return new StringConcatHelper.Concat1(constants); } public byte stringInitCoder() { return String.COMPACT_STRINGS ? String.LATIN1 : String.UTF16; } public byte stringCoder(String str) { return str.coder(); } public String join(String prefix, String suffix, String delimiter, String[] elements, int size) { return String.join(prefix, suffix, delimiter, elements, size); } public String concat(String prefix, Object value, String suffix) { return StringConcatHelper.concat(prefix, value, suffix); } public Object classData(Class c) { return c.getClassData(); } @Override public NativeLibraries nativeLibrariesFor(ClassLoader loader) { return ClassLoader.nativeLibrariesFor(loader); } public Thread[] getAllThreads() { return Thread.getAllThreads(); } public ThreadContainer threadContainer(Thread thread) { return thread.threadContainer(); } public void start(Thread thread, ThreadContainer container) { thread.start(container); } public StackableScope headStackableScope(Thread thread) { return thread.headStackableScopes(); } public void setHeadStackableScope(StackableScope scope) { Thread.setHeadStackableScope(scope); } public Thread currentCarrierThread() { return Thread.currentCarrierThread(); } public T getCarrierThreadLocal(CarrierThreadLocal local) { return ((ThreadLocal)local).getCarrierThreadLocal(); } public void setCarrierThreadLocal(CarrierThreadLocal local, T value) { ((ThreadLocal)local).setCarrierThreadLocal(value); } public void removeCarrierThreadLocal(CarrierThreadLocal local) { ((ThreadLocal)local).removeCarrierThreadLocal(); } public Object[] scopedValueCache() { return Thread.scopedValueCache(); } public void setScopedValueCache(Object[] cache) { Thread.setScopedValueCache(cache); } public Object scopedValueBindings() { return Thread.scopedValueBindings(); } public Continuation getContinuation(Thread thread) { return thread.getContinuation(); } public void setContinuation(Thread thread, Continuation continuation) { thread.setContinuation(continuation); } public ContinuationScope virtualThreadContinuationScope() { return VirtualThread.continuationScope(); } public void parkVirtualThread() { Thread thread = Thread.currentThread(); if (thread instanceof BaseVirtualThread vthread) { vthread.park(); } else { throw new WrongThreadException(); } } public void parkVirtualThread(long nanos) { Thread thread = Thread.currentThread(); if (thread instanceof BaseVirtualThread vthread) { vthread.parkNanos(nanos); } else { throw new WrongThreadException(); } } public void unparkVirtualThread(Thread thread) { if (thread instanceof BaseVirtualThread vthread) { vthread.unpark(); } else { throw new WrongThreadException(); } } public Executor virtualThreadDefaultScheduler() { return VirtualThread.defaultScheduler(); } public StackWalker newStackWalkerInstance(Set options, ContinuationScope contScope, Continuation continuation) { return StackWalker.newInstance(options, null, contScope, continuation); } public String getLoaderNameID(ClassLoader loader) { return loader != null ? loader.nameAndId() : "null"; } @Override public void copyToSegmentRaw(String string, MemorySegment segment, long offset) { string.copyToSegmentRaw(segment, offset); } @Override public boolean bytesCompatible(String string, Charset charset) { return string.bytesCompatible(charset); } }); } }