{@code Class} has no public constructor. Instead a {@code Class} * object is constructed automatically by the Java Virtual Machine when * a class is derived from the bytes of a {@code class} file through * the invocation of one of the following methods: *
The methods of class {@code Class} expose many characteristics of a * class or interface. Most characteristics are derived from the {@code class} * file that the class loader passed to the Java Virtual Machine or * from the {@code class} file passed to {@code Lookup::defineClass} * or {@code Lookup::defineHiddenClass}. * A few characteristics are determined by the class loading environment * at run time, such as the module returned by {@link #getModule() getModule()}. * *
The following example uses a {@code Class} object to print the * class name of an object: * * {@snippet lang="java" : * void printClassName(Object obj) { * System.out.println("The class of " + obj + * " is " + obj.getClass().getName()); * }} * * It is also possible to get the {@code Class} object for a named * class or interface (or for {@code void}) using a class literal * (JLS {@jls 15.8.2}). * For example: * * {@snippet lang="java" : * System.out.println("The name of class Foo is: " + Foo.class.getName()); // @highlight substring="Foo.class" * } * *
Some methods of class {@code Class} expose whether the declaration of * a class or interface in Java source code was enclosed within * another declaration. Other methods describe how a class or interface * is situated in a {@index "nest"}. A nest is a set of * classes and interfaces, in the same run-time package, that * allow mutual access to their {@code private} members. * The classes and interfaces are known as {@index "nestmates"} * (JVMS {@jvms 4.7.29}). * One nestmate acts as the * nest host (JVMS {@jvms 4.7.28}), and enumerates the other nestmates which * belong to the nest; each of them in turn records it as the nest host. * The classes and interfaces which belong to a nest, including its host, are * determined when * {@code class} files are generated, for example, a Java compiler * will typically record a top-level class as the host of a nest where the * other members are the classes and interfaces whose declarations are * enclosed within the top-level class declaration. * *
Note that since information about the runtime representation * of a type is being generated, modifiers not present on the * originating source code or illegal on the originating source * code may be present. * * @return a string describing this {@code Class}, including * information about modifiers and type parameters * * @since 1.8 */ public String toGenericString() { if (isPrimitive()) { return toString(); } else { StringBuilder sb = new StringBuilder(); Class component = this; int arrayDepth = 0; if (isArray()) { do { arrayDepth++; component = component.getComponentType(); } while (component.isArray()); sb.append(component.getName()); } else { // Class modifiers are a superset of interface modifiers int modifiers = getModifiers() & Modifier.classModifiers(); if (modifiers != 0) { sb.append(Modifier.toString(modifiers)); sb.append(' '); } // A class cannot be strictfp and sealed/non-sealed so // it is sufficient to check for sealed-ness after all // modifiers are printed. addSealingInfo(modifiers, sb); if (isAnnotation()) { sb.append('@'); } if (isInterface()) { // Note: all annotation interfaces are interfaces sb.append("interface"); } else { if (isEnum()) sb.append("enum"); else if (isRecord()) sb.append("record"); else sb.append("class"); } sb.append(' '); sb.append(getName()); } TypeVariable[] typeparms = component.getTypeParameters(); if (typeparms.length > 0) { sb.append(Arrays.stream(typeparms) .map(Class::typeVarBounds) .collect(Collectors.joining(",", "<", ">"))); } if (arrayDepth > 0) sb.append("[]".repeat(arrayDepth)); return sb.toString(); } } private void addSealingInfo(int modifiers, StringBuilder sb) { // A class can be final XOR sealed XOR non-sealed. if (Modifier.isFinal(modifiers)) { return; // no-op } else { if (isSealed()) { sb.append("sealed "); return; } else { // Check for sealed ancestor, which implies this class // is non-sealed. if (hasSealedAncestor(this)) { sb.append("non-sealed "); } } } } private boolean hasSealedAncestor(Class clazz) { // From JLS 8.1.1.2: // "It is a compile-time error if a class has a sealed direct // superclass or a sealed direct superinterface, and is not // declared final, sealed, or non-sealed either explicitly or // implicitly. // Thus, an effect of the sealed keyword is to force all // direct subclasses to explicitly declare whether they are // final, sealed, or non-sealed. This avoids accidentally // exposing a sealed class hierarchy to unwanted subclassing." // Therefore, will just check direct superclass and // superinterfaces. var superclass = clazz.getSuperclass(); if (superclass != null && superclass.isSealed()) { return true; } for (var superinterface : clazz.getInterfaces()) { if (superinterface.isSealed()) { return true; } } return false; } static String typeVarBounds(TypeVariable typeVar) { Type[] bounds = typeVar.getBounds(); if (bounds.length == 1 && bounds[0].equals(Object.class)) { return typeVar.getName(); } else { return typeVar.getName() + " extends " + Arrays.stream(bounds) .map(Type::getTypeName) .collect(Collectors.joining(" & ")); } } /** * Returns the {@code Class} object associated with the class or * interface with the given string name. Invoking this method is * equivalent to: * * {@snippet lang="java" : * Class.forName(className, true, currentLoader) * } * * where {@code currentLoader} denotes the defining class loader of * the current class. * *
For example, the following code fragment returns the * runtime {@code Class} object for the class named * {@code java.lang.Thread}: * * {@snippet lang="java" : * Class t = Class.forName("java.lang.Thread"); * } *
* A call to {@code forName("X")} causes the class named * {@code X} to be initialized. * *
* In cases where this method is called from a context where there is no * caller frame on the stack (e.g. when called directly from a JNI * attached thread), the system class loader is used. * * @param className the {@linkplain ClassLoader##binary-name binary name} * of the class or the string representing an array type * @return the {@code Class} object for the class with the * specified name. * @throws LinkageError if the linkage fails * @throws ExceptionInInitializerError if the initialization provoked * by this method fails * @throws ClassNotFoundException if the class cannot be located * * @jls 12.2 Loading of Classes and Interfaces * @jls 12.3 Linking of Classes and Interfaces * @jls 12.4 Initialization of Classes and Interfaces */ @CallerSensitive public static Class forName(String className) throws ClassNotFoundException { Class caller = Reflection.getCallerClass(); return forName(className, caller); } // Caller-sensitive adapter method for reflective invocation @CallerSensitiveAdapter private static Class forName(String className, Class caller) throws ClassNotFoundException { ClassLoader loader = (caller == null) ? ClassLoader.getSystemClassLoader() : ClassLoader.getClassLoader(caller); return forName0(className, true, loader, caller); } /** * Returns the {@code Class} object associated with the class or * interface with the given string name, using the given class loader. * Given the {@linkplain ClassLoader##binary-name binary name} for a class or interface, * this method attempts to locate and load the class or interface. The specified * class loader is used to load the class or interface. If the parameter * {@code loader} is {@code null}, the class is loaded through the bootstrap * class loader. The class is initialized only if the * {@code initialize} parameter is {@code true} and if it has * not been initialized earlier. * *
This method cannot be used to obtain any of the {@code Class} objects * representing primitive types or void, hidden classes or interfaces, * or array classes whose element type is a hidden class or interface. * If {@code name} denotes a primitive type or void, for example {@code I}, * an attempt will be made to locate a user-defined class in the unnamed package * whose name is {@code I} instead. * To obtain a {@code Class} object for a named primitive type * such as {@code int} or {@code long} use {@link * #forPrimitiveName(String)}. * *
To obtain the {@code Class} object associated with an array class, * the name consists of one or more {@code '['} representing the depth * of the array nesting, followed by the element type as encoded in * {@linkplain ##nameFormat the table} specified in {@code Class.getName()}. * *
Examples: * {@snippet lang="java" : * Class threadClass = Class.forName("java.lang.Thread", false, currentLoader); * Class stringArrayClass = Class.forName("[Ljava.lang.String;", false, currentLoader); * Class intArrayClass = Class.forName("[[[I", false, currentLoader); // Class of int[][][] * Class nestedClass = Class.forName("java.lang.Character$UnicodeBlock", false, currentLoader); * Class fooClass = Class.forName("Foo", true, currentLoader); * } * *
A call to {@code getName()} on the {@code Class} object returned * from {@code forName(}N{@code )} returns N. * *
A call to {@code forName("[L}N{@code ;")} causes the element type * named N to be loaded but not initialized regardless of the value * of the {@code initialize} parameter. * * @apiNote * This method throws errors related to loading, linking or initializing * as specified in Sections {@jls 12.2}, {@jls 12.3}, and {@jls 12.4} of * The Java Language Specification. * In addition, this method does not check whether the requested class * is accessible to its caller. * * @param name the {@linkplain ClassLoader##binary-name binary name} * of the class or the string representing an array class * * @param initialize if {@code true} the class will be initialized * (which implies linking). See Section {@jls * 12.4} of The Java Language * Specification. * @param loader class loader from which the class must be loaded * @return class object representing the desired class * * @throws LinkageError if the linkage fails * @throws ExceptionInInitializerError if the initialization provoked * by this method fails * @throws ClassNotFoundException if the class cannot be located by * the specified class loader * * @see java.lang.Class#forName(String) * @see java.lang.ClassLoader * * @jls 12.2 Loading of Classes and Interfaces * @jls 12.3 Linking of Classes and Interfaces * @jls 12.4 Initialization of Classes and Interfaces * @jls 13.1 The Form of a Binary * @since 1.2 */ public static Class forName(String name, boolean initialize, ClassLoader loader) throws ClassNotFoundException { return forName0(name, initialize, loader, null); } /** Called after security check for system loader access checks have been made. */ private static native Class forName0(String name, boolean initialize, ClassLoader loader, Class caller) throws ClassNotFoundException; /** * Returns the {@code Class} with the given {@linkplain ClassLoader##binary-name * binary name} in the given module. * *
This method attempts to locate and load the class or interface. * It does not link the class, and does not run the class initializer. * If the class is not found, this method returns {@code null}.
* *If the class loader of the given module defines other modules and * the given name is a class defined in a different module, this method * returns {@code null} after the class is loaded.
* *This method does not check whether the requested class is * accessible to its caller.
* * @apiNote * This method does not support loading of array types, unlike * {@link #forName(String, boolean, ClassLoader)}. The class name must be * a binary name. This method returns {@code null} on failure rather than * throwing a {@link ClassNotFoundException}, as is done by * the {@link #forName(String, boolean, ClassLoader)} method. * * @param module A module * @param name The {@linkplain ClassLoader##binary-name binary name} * of the class * @return {@code Class} object of the given name defined in the given module; * {@code null} if not found. * * @throws NullPointerException if the given module or name is {@code null} * * @throws LinkageError if the linkage fails * * @jls 12.2 Loading of Classes and Interfaces * @jls 12.3 Linking of Classes and Interfaces * @since 9 */ public static Class forName(Module module, String name) { Objects.requireNonNull(module); Objects.requireNonNull(name); ClassLoader cl = module.getClassLoader(); if (cl != null) { return cl.loadClass(module, name); } else { return BootLoader.loadClass(module, name); } } /** * {@return the {@code Class} object associated with the * {@linkplain #isPrimitive() primitive type} of the given name} * If the argument is not the name of a primitive type, {@code * null} is returned. * * @param primitiveName the name of the primitive type to find * * @throws NullPointerException if the argument is {@code null} * * @jls 4.2 Primitive Types and Values * @jls 15.8.2 Class Literals * @since 22 */ public static Class forPrimitiveName(String primitiveName) { return switch(primitiveName) { // Integral types case "int" -> int.class; case "long" -> long.class; case "short" -> short.class; case "char" -> char.class; case "byte" -> byte.class; // Floating-point types case "float" -> float.class; case "double" -> double.class; // Other types case "boolean" -> boolean.class; case "void" -> void.class; default -> null; }; } /** * Creates a new instance of the class represented by this {@code Class} * object. The class is instantiated as if by a {@code new} * expression with an empty argument list. The class is initialized if it * has not already been initialized. * * @deprecated This method propagates any exception thrown by the * nullary constructor, including a checked exception. Use of * this method effectively bypasses the compile-time exception * checking that would otherwise be performed by the compiler. * The {@link * java.lang.reflect.Constructor#newInstance(java.lang.Object...) * Constructor.newInstance} method avoids this problem by wrapping * any exception thrown by the constructor in a (checked) {@link * java.lang.reflect.InvocationTargetException}. * *The call
*
* {@snippet lang="java" :
* clazz.newInstance()
* }
*
* can be replaced by
*
* {@snippet lang="java" :
* clazz.getDeclaredConstructor().newInstance()
* }
*
* The latter sequence of calls is inferred to be able to throw
* the additional exception types {@link
* InvocationTargetException} and {@link
* NoSuchMethodException}. Both of these exception types are
* subclasses of {@link ReflectiveOperationException}.
*
* @return a newly allocated instance of the class represented by this
* object.
* @throws IllegalAccessException if the class or its nullary
* constructor is not accessible.
* @throws InstantiationException
* if this {@code Class} represents an abstract class,
* an interface, an array class, a primitive type, or void;
* or if the class has no nullary constructor;
* or if the instantiation fails for some other reason.
* @throws ExceptionInInitializerError if the initialization
* provoked by this method fails.
*/
@CallerSensitive
@Deprecated(since="9")
public T newInstance()
throws InstantiationException, IllegalAccessException
{
// Constructor lookup
Constructor Specifically, if this {@code Class} object represents a
* declared class, this method returns {@code true} if the specified
* {@code Object} argument is an instance of the represented class (or
* of any of its subclasses); it returns {@code false} otherwise. If
* this {@code Class} object represents an array class, this method
* returns {@code true} if the specified {@code Object} argument
* can be converted to an object of the array class by an identity
* conversion or by a widening reference conversion; it returns
* {@code false} otherwise. If this {@code Class} object
* represents an interface, this method returns {@code true} if the
* class or any superclass of the specified {@code Object} argument
* implements this interface; it returns {@code false} otherwise. If
* this {@code Class} object represents a primitive type, this method
* returns {@code false}.
*
* @param obj the object to check
* @return true if {@code obj} is an instance of this class
*
* @since 1.1
*/
@IntrinsicCandidate
public native boolean isInstance(Object obj);
/**
* Determines if the class or interface represented by this
* {@code Class} object is either the same as, or is a superclass or
* superinterface of, the class or interface represented by the specified
* {@code Class} parameter. It returns {@code true} if so;
* otherwise it returns {@code false}. If this {@code Class}
* object represents a primitive type, this method returns
* {@code true} if the specified {@code Class} parameter is
* exactly this {@code Class} object; otherwise it returns
* {@code false}.
*
* Specifically, this method tests whether the type represented by the
* specified {@code Class} parameter can be converted to the type
* represented by this {@code Class} object via an identity conversion
* or via a widening reference conversion. See The Java Language
* Specification, sections {@jls 5.1.1} and {@jls 5.1.4},
* for details.
*
* @param cls the {@code Class} object to be checked
* @return the {@code boolean} value indicating whether objects of the
* type {@code cls} can be assigned to objects of this class
* @throws NullPointerException if the specified Class parameter is
* null.
* @since 1.1
*/
@IntrinsicCandidate
public native boolean isAssignableFrom(Class cls);
/**
* Determines if this {@code Class} object represents an
* interface type.
*
* @return {@code true} if this {@code Class} object represents an interface;
* {@code false} otherwise.
*/
public boolean isInterface() {
return Modifier.isInterface(modifiers);
}
/**
* Determines if this {@code Class} object represents an array class.
*
* @return {@code true} if this {@code Class} object represents an array class;
* {@code false} otherwise.
* @since 1.1
*/
public boolean isArray() {
return componentType != null;
}
/**
* Determines if this {@code Class} object represents a primitive
* type or void.
*
* There are nine predefined {@code Class} objects to
* represent the eight primitive types and void. These are
* created by the Java Virtual Machine, and have the same
* {@linkplain #getName() names} as the primitive types that they
* represent, namely {@code boolean}, {@code byte}, {@code char},
* {@code short}, {@code int}, {@code long}, {@code float}, and
* {@code double}.
*
* No other class objects are considered primitive.
*
* @apiNote
* A {@code Class} object represented by a primitive type can be
* accessed via the {@code TYPE} public static final variables
* defined in the primitive wrapper classes such as {@link
* java.lang.Integer#TYPE Integer.TYPE}. In the Java programming
* language, the objects may be referred to by a class literal
* expression such as {@code int.class}. The {@code Class} object
* for void can be expressed as {@code void.class} or {@link
* java.lang.Void#TYPE Void.TYPE}.
*
* @return true if and only if this class represents a primitive type
*
* @see java.lang.Boolean#TYPE
* @see java.lang.Character#TYPE
* @see java.lang.Byte#TYPE
* @see java.lang.Short#TYPE
* @see java.lang.Integer#TYPE
* @see java.lang.Long#TYPE
* @see java.lang.Float#TYPE
* @see java.lang.Double#TYPE
* @see java.lang.Void#TYPE
* @since 1.1
* @jls 15.8.2 Class Literals
*/
public boolean isPrimitive() {
return primitive;
}
/**
* Returns true if this {@code Class} object represents an annotation
* interface. Note that if this method returns true, {@link #isInterface()}
* would also return true, as all annotation interfaces are also interfaces.
*
* @return {@code true} if this {@code Class} object represents an annotation
* interface; {@code false} otherwise
* @since 1.5
*/
public boolean isAnnotation() {
return (getModifiers() & ANNOTATION) != 0;
}
/**
*{@return {@code true} if and only if this class has the synthetic modifier
* bit set}
*
* @jls 13.1 The Form of a Binary
* @jvms 4.1 The {@code ClassFile} Structure
* @see Java
* programming language and JVM modeling in core reflection
* @since 1.5
*/
public boolean isSynthetic() {
return (getModifiers() & SYNTHETIC) != 0;
}
/**
* Returns the name of the entity (class, interface, array class,
* primitive type, or void) represented by this {@code Class} object.
*
* If this {@code Class} object represents a class or interface,
* not an array class, then:
* If this {@code Class} object represents an array class, then
* the result is a string consisting of one or more '{@code [}' characters
* representing the depth of the array nesting, followed by the element
* type as encoded using the following table:
*
* If this {@code Class} object represents a primitive type or {@code void},
* then the result is a string with the same spelling as the Java language
* keyword which corresponds to the primitive type or {@code void}.
*
* Examples:
* If this {@code Class} object
* represents a primitive type or void, null is returned.
*
* @return the class loader that loaded the class or interface
* represented by this {@code Class} object.
* @see java.lang.ClassLoader
*/
public ClassLoader getClassLoader() {
return classLoader;
}
// Package-private to allow ClassLoader access
ClassLoader getClassLoader0() { return classLoader; }
/**
* Returns the module that this class or interface is a member of.
*
* If this class represents an array type then this method returns the
* {@code Module} for the element type. If this class represents a
* primitive type or void, then the {@code Module} object for the
* {@code java.base} module is returned.
*
* If this class is in an unnamed module then the {@linkplain
* ClassLoader#getUnnamedModule() unnamed} {@code Module} of the class
* loader for this class is returned.
*
* @return the module that this class or interface is a member of
*
* @since 9
*/
public Module getModule() {
return module;
}
// set by VM
@Stable
private transient Module module;
// Initialized in JVM not by private constructor
// This field is filtered from reflection access, i.e. getDeclaredField
// will throw NoSuchFieldException
private final ClassLoader classLoader;
private transient Object classData; // Set by VM
private transient Object[] signers; // Read by VM, mutable
private final transient char modifiers; // Set by the VM
private final transient boolean primitive; // Set by the VM if the Class is a primitive type.
// package-private
Object getClassData() {
return classData;
}
/**
* Returns an array of {@code TypeVariable} objects that represent the
* type variables declared by the generic declaration represented by this
* {@code GenericDeclaration} object, in declaration order. Returns an
* array of length 0 if the underlying generic declaration declares no type
* variables.
*
* @return an array of {@code TypeVariable} objects that represent
* the type variables declared by this generic declaration
* @throws java.lang.reflect.GenericSignatureFormatError if the generic
* signature of this generic declaration does not conform to
* the format specified in section {@jvms 4.7.9} of
* The Java Virtual Machine Specification
* @since 1.5
*/
@SuppressWarnings("unchecked")
public TypeVariable If the superclass is a parameterized type, the {@code Type}
* object returned must accurately reflect the actual type
* arguments used in the source code. The parameterized type
* representing the superclass is created if it had not been
* created before. See the declaration of {@link
* java.lang.reflect.ParameterizedType ParameterizedType} for the
* semantics of the creation process for parameterized types. If
* this {@code Class} object represents either the {@code Object}
* class, an interface, a primitive type, or void, then null is
* returned. If this {@code Class} object represents an array class
* then the {@code Class} object representing the {@code Object} class is
* returned.
*
* @throws java.lang.reflect.GenericSignatureFormatError if the generic
* class signature does not conform to the format specified in
* section {@jvms 4.7.9} of The Java Virtual
* Machine Specification
* @throws TypeNotPresentException if the generic superclass
* refers to a non-existent type declaration
* @throws java.lang.reflect.MalformedParameterizedTypeException if the
* generic superclass refers to a parameterized type that cannot be
* instantiated for any reason
* @return the direct superclass of the class represented by this {@code Class} object
* @since 1.5
*/
public Type getGenericSuperclass() {
ClassRepository info = getGenericInfo();
if (info == null) {
return getSuperclass();
}
// Historical irregularity:
// Generic signature marks interfaces with superclass = Object
// but this API returns null for interfaces
if (isInterface()) {
return null;
}
return info.getSuperclass();
}
/**
* Gets the package of this class.
*
* If this class represents an array type, a primitive type or void,
* this method returns {@code null}.
*
* @return the package of this class.
*/
public Package getPackage() {
if (isPrimitive() || isArray()) {
return null;
}
ClassLoader cl = classLoader;
return cl != null ? cl.definePackage(this)
: BootLoader.definePackage(this);
}
/**
* Returns the fully qualified package name.
*
* If this class is a top level class, then this method returns the fully
* qualified name of the package that the class is a member of, or the
* empty string if the class is in an unnamed package.
*
* If this class is a member class, then this method is equivalent to
* invoking {@code getPackageName()} on the {@linkplain #getEnclosingClass
* enclosing class}.
*
* If this class is a {@linkplain #isLocalClass local class} or an {@linkplain
* #isAnonymousClass() anonymous class}, then this method is equivalent to
* invoking {@code getPackageName()} on the {@linkplain #getDeclaringClass
* declaring class} of the {@linkplain #getEnclosingMethod enclosing method} or
* {@linkplain #getEnclosingConstructor enclosing constructor}.
*
* If this class represents an array type then this method returns the
* package name of the element type. If this class represents a primitive
* type or void then the package name "{@code java.lang}" is returned.
*
* @return the fully qualified package name
*
* @since 9
* @jls 6.7 Fully Qualified Names and Canonical Names
*/
public String getPackageName() {
String pn = this.packageName;
if (pn == null) {
Class c = isArray() ? elementType() : this;
if (c.isPrimitive()) {
pn = "java.lang";
} else {
String cn = c.getName();
int dot = cn.lastIndexOf('.');
pn = (dot != -1) ? cn.substring(0, dot).intern() : "";
}
this.packageName = pn;
}
return pn;
}
// cached package name
private transient String packageName;
/**
* Returns the interfaces directly implemented by the class or interface
* represented by this {@code Class} object.
*
* If this {@code Class} object represents a class, the return value is an array
* containing objects representing all interfaces directly implemented by
* the class. The order of the interface objects in the array corresponds
* to the order of the interface names in the {@code implements} clause of
* the declaration of the class represented by this {@code Class} object. For example,
* given the declaration:
* If this {@code Class} object represents an interface, the array contains objects
* representing all interfaces directly extended by the interface. The
* order of the interface objects in the array corresponds to the order of
* the interface names in the {@code extends} clause of the declaration of
* the interface represented by this {@code Class} object.
*
* If this {@code Class} object represents a class or interface that implements no
* interfaces, the method returns an array of length 0.
*
* If this {@code Class} object represents a primitive type or void, the method
* returns an array of length 0.
*
* If this {@code Class} object represents an array type, the
* interfaces {@code Cloneable} and {@code java.io.Serializable} are
* returned in that order.
*
* @return an array of interfaces directly implemented by this class
*/
public Class[] getInterfaces() {
// defensively copy before handing over to user code
return getInterfaces(true);
}
private Class[] getInterfaces(boolean cloneArray) {
ReflectionData If a superinterface is a parameterized type, the
* {@code Type} object returned for it must accurately reflect
* the actual type arguments used in the source code. The
* parameterized type representing each superinterface is created
* if it had not been created before. See the declaration of
* {@link java.lang.reflect.ParameterizedType ParameterizedType}
* for the semantics of the creation process for parameterized
* types.
*
* If this {@code Class} object represents a class, the return value is an array
* containing objects representing all interfaces directly implemented by
* the class. The order of the interface objects in the array corresponds
* to the order of the interface names in the {@code implements} clause of
* the declaration of the class represented by this {@code Class} object.
*
* If this {@code Class} object represents an interface, the array contains objects
* representing all interfaces directly extended by the interface. The
* order of the interface objects in the array corresponds to the order of
* the interface names in the {@code extends} clause of the declaration of
* the interface represented by this {@code Class} object.
*
* If this {@code Class} object represents a class or interface that implements no
* interfaces, the method returns an array of length 0.
*
* If this {@code Class} object represents a primitive type or void, the method
* returns an array of length 0.
*
* If this {@code Class} object represents an array type, the
* interfaces {@code Cloneable} and {@code java.io.Serializable} are
* returned in that order.
*
* @throws java.lang.reflect.GenericSignatureFormatError
* if the generic class signature does not conform to the
* format specified in section {@jvms 4.7.9} of The
* Java Virtual Machine Specification
* @throws TypeNotPresentException if any of the generic
* superinterfaces refers to a non-existent type declaration
* @throws java.lang.reflect.MalformedParameterizedTypeException
* if any of the generic superinterfaces refer to a parameterized
* type that cannot be instantiated for any reason
* @return an array of interfaces directly implemented by this class
* @since 1.5
*/
public Type[] getGenericInterfaces() {
ClassRepository info = getGenericInfo();
return (info == null) ? getInterfaces() : info.getSuperInterfaces();
}
/**
* Returns the {@code Class} representing the component type of an
* array. If this class does not represent an array class this method
* returns null.
*
* @return the {@code Class} representing the component type of this
* class if this class is an array
* @see java.lang.reflect.Array
* @since 1.1
*/
public Class getComponentType() {
return componentType;
}
// The componentType field's null value is the sole indication that the class
// is an array - see isArray().
private transient final Class componentType;
/*
* Returns the {@code Class} representing the element type of an array class.
* If this class does not represent an array class, then this method returns
* {@code null}.
*/
private Class elementType() {
if (!isArray()) return null;
Class c = this;
while (c.isArray()) {
c = c.getComponentType();
}
return c;
}
/**
* Returns the Java language modifiers for this class or interface, encoded
* in an integer. The modifiers consist of the Java Virtual Machine's
* constants for {@code public}, {@code protected},
* {@code private}, {@code final}, {@code static},
* {@code abstract} and {@code interface}; they should be decoded
* using the methods of class {@code Modifier}.
*
* If the underlying class is an array class:
* The modifier encodings are defined in section {@jvms 4.1}
* of The Java Virtual Machine Specification.
*
* @return the {@code int} representing the modifiers for this class
* @see java.lang.reflect.Modifier
* @see #accessFlags()
* @see Java
* programming language and JVM modeling in core reflection
* @since 1.1
* @jls 8.1.1 Class Modifiers
* @jls 9.1.1 Interface Modifiers
* @jvms 4.1 The {@code ClassFile} Structure
*/
public int getModifiers() { return modifiers; }
/**
* {@return an unmodifiable set of the {@linkplain AccessFlag access
* flags} for this class, possibly empty}
*
* If the underlying class is an array class:
* The simple name of an {@linkplain #isArray() array class} is the simple name of the
* component type with "[]" appended. In particular the simple
* name of an array class whose component type is anonymous is "[]".
*
* @return the simple name of the underlying class
* @since 1.5
*/
public String getSimpleName() {
ReflectionData An array type has a canonical name if and only if its
* component type has a canonical name. When an array type has a
* canonical name, it is equal to the canonical name of the
* component type followed by "{@code []}".
*
* @return the canonical name of the underlying class if it exists, and
* {@code null} otherwise.
* @jls 6.7 Fully Qualified Names and Canonical Names
* @since 1.5
*/
public String getCanonicalName() {
ReflectionData If this {@code Class} object represents a class or interface with
* no accessible public fields, then this method returns an array of length
* 0.
*
* If this {@code Class} object represents a class, then this method
* returns the public fields of the class and of all its superclasses and
* superinterfaces.
*
* If this {@code Class} object represents an interface, then this
* method returns the fields of the interface and of all its
* superinterfaces.
*
* If this {@code Class} object represents an array type, a primitive
* type, or void, then this method returns an array of length 0.
*
* The elements in the returned array are not sorted and are not in any
* particular order.
*
* @return the array of {@code Field} objects representing the
* public fields
*
* @since 1.1
* @jls 8.2 Class Members
* @jls 8.3 Field Declarations
*/
public Field[] getFields() {
return copyFields(privateGetPublicFields());
}
/**
* Returns an array containing {@code Method} objects reflecting all the
* public methods of the class or interface represented by this {@code
* Class} object, including those declared by the class or interface and
* those inherited from superclasses and superinterfaces.
*
* If this {@code Class} object represents an array type, then the
* returned array has a {@code Method} object for each of the public
* methods inherited by the array type from {@code Object}. It does not
* contain a {@code Method} object for {@code clone()}.
*
* If this {@code Class} object represents an interface then the
* returned array does not contain any implicitly declared methods from
* {@code Object}. Therefore, if no methods are explicitly declared in
* this interface or any of its superinterfaces then the returned array
* has length 0. (Note that a {@code Class} object which represents a class
* always has public methods, inherited from {@code Object}.)
*
* The returned array never contains methods with names {@value
* ConstantDescs#INIT_NAME} or {@value ConstantDescs#CLASS_INIT_NAME}.
*
* The elements in the returned array are not sorted and are not in any
* particular order.
*
* Generally, the result is computed as with the following 4 step algorithm.
* Let C be the class or interface represented by this {@code Class} object:
* The field to be reflected is determined by the algorithm that
* follows. Let C be the class or interface represented by this {@code Class} object:
*
* If this {@code Class} object represents an array type, then this
* method does not find the {@code length} field of the array type.
*
* @param name the field name
* @return the {@code Field} object of this class specified by
* {@code name}
* @throws NoSuchFieldException if a field with the specified name is
* not found.
* @throws NullPointerException if {@code name} is {@code null}
*
* @since 1.1
* @jls 8.2 Class Members
* @jls 8.3 Field Declarations
*/
public Field getField(String name) throws NoSuchFieldException {
Objects.requireNonNull(name);
Field field = getField0(name);
if (field == null) {
throw new NoSuchFieldException(name);
}
return getReflectionFactory().copyField(field);
}
/**
* Returns a {@code Method} object that reflects the specified public
* member method of the class or interface represented by this
* {@code Class} object. The {@code name} parameter is a
* {@code String} specifying the simple name of the desired method. The
* {@code parameterTypes} parameter is an array of {@code Class}
* objects that identify the method's formal parameter types, in declared
* order. If {@code parameterTypes} is {@code null}, it is
* treated as if it were an empty array.
*
* If this {@code Class} object represents an array type, then this
* method finds any public method inherited by the array type from
* {@code Object} except method {@code clone()}.
*
* If this {@code Class} object represents an interface then this
* method does not find any implicitly declared method from
* {@code Object}. Therefore, if no methods are explicitly declared in
* this interface or any of its superinterfaces, then this method does not
* find any method.
*
* This method does not find any method with name {@value
* ConstantDescs#INIT_NAME} or {@value ConstantDescs#CLASS_INIT_NAME}.
*
* Generally, the method to be reflected is determined by the 4 step
* algorithm that follows.
* Let C be the class or interface represented by this {@code Class} object:
* The constructor to reflect is the public constructor of the class
* represented by this {@code Class} object whose formal parameter
* types match those specified by {@code parameterTypes}.
*
* @param parameterTypes the parameter array
* @return the {@code Constructor} object of the public constructor that
* matches the specified {@code parameterTypes}
* @throws NoSuchMethodException if a matching constructor is not found,
* including when this {@code Class} object represents
* an interface, a primitive type, an array class, or void.
*
* @see #getDeclaredConstructor(Class[])
* @since 1.1
*/
public Constructor If this {@code Class} object represents a class or interface with no
* declared fields, then this method returns an array of length 0.
*
* If this {@code Class} object represents an array type, a primitive
* type, or void, then this method returns an array of length 0.
*
* The elements in the returned array are not sorted and are not in any
* particular order.
*
* @return the array of {@code Field} objects representing all the
* declared fields of this class
*
* @since 1.1
* @jls 8.2 Class Members
* @jls 8.3 Field Declarations
*/
public Field[] getDeclaredFields() {
return copyFields(privateGetDeclaredFields(false));
}
/**
* Returns an array of {@code RecordComponent} objects representing all the
* record components of this record class, or {@code null} if this class is
* not a record class.
*
* The components are returned in the same order that they are declared
* in the record header. The array is empty if this record class has no
* components. If the class is not a record class, that is {@link
* #isRecord()} returns {@code false}, then this method returns {@code null}.
* Conversely, if {@link #isRecord()} returns {@code true}, then this method
* returns a non-null value.
*
* @apiNote
* The following method can be used to find the record canonical constructor:
*
* {@snippet lang="java" :
* static If this {@code Class} object represents a class or interface that
* has multiple declared methods with the same name and parameter types,
* but different return types, then the returned array has a {@code Method}
* object for each such method.
*
* If this {@code Class} object represents a class or interface that
* has a class initialization method {@value ConstantDescs#CLASS_INIT_NAME},
* then the returned array does not have a corresponding {@code
* Method} object.
*
* If this {@code Class} object represents a class or interface with no
* declared methods, then the returned array has length 0.
*
* If this {@code Class} object represents an array type, a primitive
* type, or void, then the returned array has length 0.
*
* The elements in the returned array are not sorted and are not in any
* particular order.
*
* @return the array of {@code Method} objects representing all the
* declared methods of this class
*
* @jls 8.2 Class Members
* @jls 8.4 Method Declarations
* @see Java
* programming language and JVM modeling in core reflection
* @since 1.1
*/
public Method[] getDeclaredMethods() {
return copyMethods(privateGetDeclaredMethods(false));
}
/**
* Returns an array of {@code Constructor} objects reflecting all the
* constructors implicitly or explicitly declared by the class represented by this
* {@code Class} object. These are public, protected, default
* (package) access, and private constructors. The elements in the array
* returned are not sorted and are not in any particular order. If the
* class has a default constructor (JLS {@jls 8.8.9}), it is included in the returned array.
* If a record class has a canonical constructor (JLS {@jls
* 8.10.4.1}, {@jls 8.10.4.2}), it is included in the returned array.
*
* This method returns an array of length 0 if this {@code Class}
* object represents an interface, a primitive type, an array class, or
* void.
*
* @return the array of {@code Constructor} objects representing all the
* declared constructors of this class
*
* @since 1.1
* @see #getConstructors()
* @jls 8.8 Constructor Declarations
*/
public Constructor[] getDeclaredConstructors() {
return copyConstructors(privateGetDeclaredConstructors(false));
}
/**
* Returns a {@code Field} object that reflects the specified declared
* field of the class or interface represented by this {@code Class}
* object. The {@code name} parameter is a {@code String} that specifies
* the simple name of the desired field.
*
* If this {@code Class} object represents an array type, then this
* method does not find the {@code length} field of the array type.
*
* @param name the name of the field
* @return the {@code Field} object for the specified field in this
* class
* @throws NoSuchFieldException if a field with the specified name is
* not found.
* @throws NullPointerException if {@code name} is {@code null}
*
* @since 1.1
* @jls 8.2 Class Members
* @jls 8.3 Field Declarations
*/
public Field getDeclaredField(String name) throws NoSuchFieldException {
Objects.requireNonNull(name);
Field field = searchFields(privateGetDeclaredFields(false), name);
if (field == null) {
throw new NoSuchFieldException(name);
}
return getReflectionFactory().copyField(field);
}
/**
* Returns a {@code Method} object that reflects the specified
* declared method of the class or interface represented by this
* {@code Class} object. The {@code name} parameter is a
* {@code String} that specifies the simple name of the desired
* method, and the {@code parameterTypes} parameter is an array of
* {@code Class} objects that identify the method's formal parameter
* types, in declared order. If more than one method with the same
* parameter types is declared in a class, and one of these methods has a
* return type that is more specific than any of the others, that method is
* returned; otherwise one of the methods is chosen arbitrarily. If the
* name is {@value ConstantDescs#INIT_NAME} or {@value
* ConstantDescs#CLASS_INIT_NAME} a {@code NoSuchMethodException}
* is raised.
*
* If this {@code Class} object represents an array type, then this
* method does not find the {@code clone()} method.
*
* @param name the name of the method
* @param parameterTypes the parameter array
* @return the {@code Method} object for the method of this class
* matching the specified name and parameters
* @throws NoSuchMethodException if a matching method is not found.
* @throws NullPointerException if {@code name} is {@code null}
*
* @jls 8.2 Class Members
* @jls 8.4 Method Declarations
* @since 1.1
*/
public Method getDeclaredMethod(String name, Class... parameterTypes)
throws NoSuchMethodException {
Objects.requireNonNull(name);
Method method = searchMethods(privateGetDeclaredMethods(false), name, parameterTypes);
if (method == null) {
throw new NoSuchMethodException(methodToString(name, parameterTypes));
}
return getReflectionFactory().copyMethod(method);
}
/**
* Returns the list of {@code Method} objects for the declared public
* methods of this class or interface that have the specified method name
* and parameter types.
*
* @param name the name of the method
* @param parameterTypes the parameter array
* @return the list of {@code Method} objects for the public methods of
* this class matching the specified name and parameters
*/
List If this class is in a named {@link Module Module} then this method
* will attempt to find the resource in the module. This is done by
* delegating to the module's class loader {@link
* ClassLoader#findResource(String,String) findResource(String,String)}
* method, invoking it with the module name and the absolute name of the
* resource. Resources in named modules are subject to the rules for
* encapsulation specified in the {@code Module} {@link
* Module#getResourceAsStream getResourceAsStream} method and so this
* method returns {@code null} when the resource is a
* non-"{@code .class}" resource in a package that is not open to the
* caller's module.
*
* Otherwise, if this class is not in a named module then the rules for
* searching resources associated with a given class are implemented by the
* defining {@linkplain ClassLoader class loader} of the class. This method
* delegates to this {@code Class} object's class loader.
* If this {@code Class} object was loaded by the bootstrap class loader,
* the method delegates to {@link ClassLoader#getSystemResourceAsStream}.
*
* Before delegation, an absolute resource name is constructed from the
* given resource name using this algorithm:
*
* Where the {@code modified_package_name} is the package name of this
* object with {@code '/'} substituted for {@code '.'}
* ( If this class is in a named {@link Module Module} then this method
* will attempt to find the resource in the module. This is done by
* delegating to the module's class loader {@link
* ClassLoader#findResource(String,String) findResource(String,String)}
* method, invoking it with the module name and the absolute name of the
* resource. Resources in named modules are subject to the rules for
* encapsulation specified in the {@code Module} {@link
* Module#getResourceAsStream getResourceAsStream} method and so this
* method returns {@code null} when the resource is a
* non-"{@code .class}" resource in a package that is not open to the
* caller's module.
*
* Otherwise, if this class is not in a named module then the rules for
* searching resources associated with a given class are implemented by the
* defining {@linkplain ClassLoader class loader} of the class. This method
* delegates to this {@code Class} object's class loader.
* If this {@code Class} object was loaded by the bootstrap class loader,
* the method delegates to {@link ClassLoader#getSystemResource}.
*
* Before delegation, an absolute resource name is constructed from the
* given resource name using this algorithm:
*
* Where the {@code modified_package_name} is the package name of this
* object with {@code '/'} substituted for {@code '.'}
* ( The {@linkplain #getSuperclass() direct superclass} of a record
* class is {@code java.lang.Record}. A record class is {@linkplain
* Modifier#FINAL final}. A record class has (possibly zero) record
* components; {@link #getRecordComponents()} returns a non-null but
* possibly empty value for a record.
*
* Note that class {@link Record} is not a record class and thus
* invoking this method on class {@code Record} returns {@code false}.
*
* @return true if and only if this class is a record class, otherwise false
* @jls 8.10 Record Classes
* @since 16
*/
public boolean isRecord() {
// this superclass and final modifier check is not strictly necessary
// they are intrinsified and serve as a fast-path check
return getSuperclass() == java.lang.Record.class &&
(this.getModifiers() & Modifier.FINAL) != 0 &&
isRecord0();
}
// Fetches the factory for reflective objects
private static ReflectionFactory getReflectionFactory() {
var factory = reflectionFactory;
if (factory != null) {
return factory;
}
return reflectionFactory = ReflectionFactory.getReflectionFactory();
}
private static ReflectionFactory reflectionFactory;
/**
* When CDS is enabled, the Class class may be aot-initialized. However,
* we can't archive reflectionFactory, so we reset it to null, so it
* will be allocated again at runtime.
*/
private static void resetArchivedStates() {
reflectionFactory = null;
}
/**
* Returns the elements of this enum class or null if this
* Class object does not represent an enum class.
*
* @return an array containing the values comprising the enum class
* represented by this {@code Class} object in the order they're
* declared, or null if this {@code Class} object does not
* represent an enum class
* @since 1.5
* @jls 8.9.1 Enum Constants
*/
public T[] getEnumConstants() {
T[] values = getEnumConstantsShared();
return (values != null) ? values.clone() : null;
}
/**
* Returns the elements of this enum class or null if this
* Class object does not represent an enum class;
* identical to getEnumConstants except that the result is
* uncloned, cached, and shared by all callers.
*/
T[] getEnumConstantsShared() {
T[] constants = enumConstants;
if (constants == null) {
if (!isEnum()) return null;
try {
final Method values = getMethod("values");
values.setAccessible(true);
@SuppressWarnings("unchecked")
T[] temporaryConstants = (T[])values.invoke(null);
enumConstants = constants = temporaryConstants;
}
// These can happen when users concoct enum-like classes
// that don't comply with the enum spec.
catch (InvocationTargetException | NoSuchMethodException |
IllegalAccessException | NullPointerException |
ClassCastException ex) { return null; }
}
return constants;
}
private transient volatile T[] enumConstants;
/**
* Returns a map from simple name to enum constant. This package-private
* method is used internally by Enum to implement
* {@code public static This method is useful when a client needs to "narrow" the type of
* a {@code Class} object to pass it to an API that restricts the
* {@code Class} objects that it is willing to accept. A cast would
* generate a compile-time warning, as the correctness of the cast
* could not be checked at runtime (because generic types are implemented
* by erasure).
*
* @param the type to cast this {@code Class} object to
* @param clazz the class of the type to cast this {@code Class} object to
* @return this {@code Class} object, cast to represent a subclass of
* the specified class object.
* @throws ClassCastException if this {@code Class} object does not
* represent a subclass of the specified class (here "subclass" includes
* the class itself).
* @since 1.5
*/
@SuppressWarnings("unchecked")
public Class asSubclass(Class clazz) {
if (clazz.isAssignableFrom(this))
return (Class) this;
else
throw new ClassCastException(this.toString());
}
/**
* {@inheritDoc}
* Note that any annotation returned by this method is a
* declaration annotation.
*
* @throws NullPointerException {@inheritDoc}
* @since 1.5
*/
@Override
@SuppressWarnings("unchecked")
public A getAnnotation(Class annotationClass) {
Objects.requireNonNull(annotationClass);
return (A) annotationData().annotations.get(annotationClass);
}
/**
* {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @since 1.5
*/
@Override
public boolean isAnnotationPresent(Class annotationClass) {
return GenericDeclaration.super.isAnnotationPresent(annotationClass);
}
/**
* {@inheritDoc}
* Note that any annotations returned by this method are
* declaration annotations.
*
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
public A[] getAnnotationsByType(Class annotationClass) {
Objects.requireNonNull(annotationClass);
AnnotationData annotationData = annotationData();
return AnnotationSupport.getAssociatedAnnotations(annotationData.declaredAnnotations,
this,
annotationClass);
}
/**
* {@inheritDoc}
* Note that any annotations returned by this method are
* declaration annotations.
*
* @since 1.5
*/
@Override
public Annotation[] getAnnotations() {
return AnnotationParser.toArray(annotationData().annotations);
}
/**
* {@inheritDoc}
* Note that any annotation returned by this method is a
* declaration annotation.
*
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
@SuppressWarnings("unchecked")
public A getDeclaredAnnotation(Class annotationClass) {
Objects.requireNonNull(annotationClass);
return (A) annotationData().declaredAnnotations.get(annotationClass);
}
/**
* {@inheritDoc}
* Note that any annotations returned by this method are
* declaration annotations.
*
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
public A[] getDeclaredAnnotationsByType(Class annotationClass) {
Objects.requireNonNull(annotationClass);
return AnnotationSupport.getDirectlyAndIndirectlyPresent(annotationData().declaredAnnotations,
annotationClass);
}
/**
* {@inheritDoc}
* Note that any annotations returned by this method are
* declaration annotations.
*
* @since 1.5
*/
@Override
public Annotation[] getDeclaredAnnotations() {
return AnnotationParser.toArray(annotationData().declaredAnnotations);
}
// annotation data that might get invalidated when JVM TI RedefineClasses() is called
private static class AnnotationData {
final Map If this {@code Class} object represents a class whose declaration
* does not explicitly indicate an annotated superclass, then the return
* value is an {@code AnnotatedType} object representing an element with no
* annotations.
*
* If this {@code Class} represents either the {@code Object} class, an
* interface type, an array type, a primitive type, or void, the return
* value is {@code null}.
*
* @return an object representing the superclass
* @since 1.8
*/
public AnnotatedType getAnnotatedSuperclass() {
if (this == Object.class ||
isInterface() ||
isArray() ||
isPrimitive() ||
this == Void.TYPE) {
return null;
}
return TypeAnnotationParser.buildAnnotatedSuperclass(getRawTypeAnnotations(), getConstantPool(), this);
}
/**
* Returns an array of {@code AnnotatedType} objects that represent the use
* of types to specify superinterfaces of the entity represented by this
* {@code Class} object. (The use of type Foo to specify a
* superinterface in '... implements Foo' is distinct from the
* declaration of interface Foo.)
*
* If this {@code Class} object represents a class, the return value is
* an array containing objects representing the uses of interface types to
* specify interfaces implemented by the class. The order of the objects in
* the array corresponds to the order of the interface types used in the
* 'implements' clause of the declaration of this {@code Class} object.
*
* If this {@code Class} object represents an interface, the return
* value is an array containing objects representing the uses of interface
* types to specify interfaces directly extended by the interface. The
* order of the objects in the array corresponds to the order of the
* interface types used in the 'extends' clause of the declaration of this
* {@code Class} object.
*
* If this {@code Class} object represents a class or interface whose
* declaration does not explicitly indicate any annotated superinterfaces,
* the return value is an array of length 0.
*
* If this {@code Class} object represents either the {@code Object}
* class, an array type, a primitive type, or void, the return value is an
* array of length 0.
*
* @return an array representing the superinterfaces
* @since 1.8
*/
public AnnotatedType[] getAnnotatedInterfaces() {
return TypeAnnotationParser.buildAnnotatedInterfaces(getRawTypeAnnotations(), getConstantPool(), this);
}
private native Class getNestHost0();
/**
* Returns the nest host of the nest to which the class
* or interface represented by this {@code Class} object belongs.
* Every class and interface belongs to exactly one nest.
*
* If the nest host of this class or interface has previously
* been determined, then this method returns the nest host.
* If the nest host of this class or interface has
* not previously been determined, then this method determines the nest
* host using the algorithm of JVMS 5.4.4, and returns it.
*
* Often, a class or interface belongs to a nest consisting only of itself,
* in which case this method returns {@code this} to indicate that the class
* or interface is the nest host.
*
* If this {@code Class} object represents a primitive type, an array type,
* or {@code void}, then this method returns {@code this},
* indicating that the represented entity belongs to the nest consisting only of
* itself, and is the nest host.
*
* @return the nest host of this class or interface
*
* @since 11
* @jvms 4.7.28 The {@code NestHost} Attribute
* @jvms 4.7.29 The {@code NestMembers} Attribute
* @jvms 5.4.4 Access Control
*/
public Class getNestHost() {
if (isPrimitive() || isArray()) {
return this;
}
return getNestHost0();
}
/**
* Determines if the given {@code Class} is a nestmate of the
* class or interface represented by this {@code Class} object.
* Two classes or interfaces are nestmates
* if they have the same {@linkplain #getNestHost() nest host}.
*
* @param c the class to check
* @return {@code true} if this class and {@code c} are members of
* the same nest; and {@code false} otherwise.
*
* @since 11
*/
public boolean isNestmateOf(Class c) {
if (this == c) {
return true;
}
if (isPrimitive() || isArray() ||
c.isPrimitive() || c.isArray()) {
return false;
}
return getNestHost() == c.getNestHost();
}
private native Class[] getNestMembers0();
/**
* Returns an array containing {@code Class} objects representing all the
* classes and interfaces that are members of the nest to which the class
* or interface represented by this {@code Class} object belongs.
*
* First, this method obtains the {@linkplain #getNestHost() nest host},
* {@code H}, of the nest to which the class or interface represented by
* this {@code Class} object belongs. The zeroth element of the returned
* array is {@code H}.
*
* Then, for each class or interface {@code C} which is recorded by {@code H}
* as being a member of its nest, this method attempts to obtain the {@code Class}
* object for {@code C} (using {@linkplain #getClassLoader() the defining class
* loader} of the current {@code Class} object), and then obtains the
* {@linkplain #getNestHost() nest host} of the nest to which {@code C} belongs.
* The classes and interfaces which are recorded by {@code H} as being members
* of its nest, and for which {@code H} can be determined as their nest host,
* are indicated by subsequent elements of the returned array. The order of
* such elements is unspecified. Duplicates are permitted.
*
* If this {@code Class} object represents a primitive type, an array type,
* or {@code void}, then this method returns a single-element array containing
* {@code this}.
*
* @apiNote
* The returned array includes only the nest members recorded in the {@code NestMembers}
* attribute, and not any hidden classes that were added to the nest via
* {@link MethodHandles.Lookup#defineHiddenClass(byte[], boolean, MethodHandles.Lookup.ClassOption...)
* Lookup::defineHiddenClass}.
*
* @return an array of all classes and interfaces in the same nest as
* this class or interface
*
* @since 11
* @see #getNestHost()
* @jvms 4.7.28 The {@code NestHost} Attribute
* @jvms 4.7.29 The {@code NestMembers} Attribute
*/
public Class[] getNestMembers() {
if (isPrimitive() || isArray()) {
return new Class[] { this };
}
Class[] members = getNestMembers0();
// Can't actually enable this due to bootstrapping issues
// assert(members.length != 1 || members[0] == this); // expected invariant from VM
return members;
}
/**
* Returns the descriptor string of the entity (class, interface, array class,
* primitive type, or {@code void}) represented by this {@code Class} object.
*
* If this {@code Class} object represents a class or interface,
* not an array class, then:
* If this {@code Class} object represents an array class, then
* the result is a string consisting of one or more '{@code [}' characters
* representing the depth of the array nesting, followed by the
* descriptor string of the element type.
* If this {@code Class} object represents a primitive type or
* {@code void}, then the result is a field descriptor string which
* is a one-letter code corresponding to a primitive type or {@code void}
* ({@code "B", "C", "D", "F", "I", "J", "S", "Z", "V"}) (JVMS {@jvms 4.3.2}).
*
* @return the descriptor string for this {@code Class} object
* @jvms 4.3.2 Field Descriptors
* @since 12
*/
@Override
public String descriptorString() {
if (isPrimitive())
return Wrapper.forPrimitiveType(this).basicTypeString();
if (isArray()) {
return "[".concat(componentType.descriptorString());
} else if (isHidden()) {
String name = getName();
int index = name.indexOf('/');
return new StringBuilder(name.length() + 2)
.append('L')
.append(name.substring(0, index).replace('.', '/'))
.append('.')
.append(name, index + 1, name.length())
.append(';')
.toString();
} else {
String name = getName().replace('.', '/');
return StringConcatHelper.concat("L", name, ";");
}
}
/**
* Returns the component type of this {@code Class}, if it describes
* an array type, or {@code null} otherwise.
*
* @implSpec
* Equivalent to {@link Class#getComponentType()}.
*
* @return a {@code Class} describing the component type, or {@code null}
* if this {@code Class} does not describe an array type
* @since 12
*/
@Override
public Class componentType() {
return getComponentType();
}
/**
* Returns a {@code Class} for an array type whose component type
* is described by this {@linkplain Class}.
*
* @throws UnsupportedOperationException if this component type is {@linkplain
* Void#TYPE void} or if the number of dimensions of the resulting array
* type would exceed 255.
* @return a {@code Class} describing the array type
* @jvms 4.3.2 Field Descriptors
* @jvms 4.4.1 The {@code CONSTANT_Class_info} Structure
* @since 12
*/
@Override
public Class arrayType() {
try {
return Array.newInstance(this, 0).getClass();
} catch (IllegalArgumentException iae) {
throw new UnsupportedOperationException(iae);
}
}
/**
* Returns a nominal descriptor for this instance, if one can be
* constructed, or an empty {@link Optional} if one cannot be.
*
* @return An {@link Optional} containing the resulting nominal descriptor,
* or an empty {@link Optional} if one cannot be constructed.
* @since 12
*/
@Override
public Optional
*
*
*
*
*
*
*
*
Element Type Encoding
* {@code boolean} {@code Z}
* {@code byte} {@code B}
* {@code char} {@code C}
* class or interface with {@linkplain ClassLoader##binary-name binary name} N
* {@code L}N{@code ;}
* {@code double} {@code D}
* {@code float} {@code F}
* {@code int} {@code I}
* {@code long} {@code J}
* {@code short} {@code S}
*
*
* @apiNote
* Distinct class objects can have the same name but different class loaders.
*
* @return the name of the class, interface, or other entity
* represented by this {@code Class} object.
* @jls 13.1 The Form of a Binary
*/
public String getName() {
String name = this.name;
return name != null ? name : initClassName();
}
// Cache the name to reduce the number of calls into the VM.
// This field would be set by VM itself during initClassName call.
private transient String name;
private native String initClassName();
/**
* Returns the class loader for the class. Some implementations may use
* null to represent the bootstrap class loader. This method will return
* null in such implementations if this class was loaded by the bootstrap
* class loader.
*
*
* String.class.getName()
* returns "java.lang.String"
* Character.UnicodeBlock.class.getName()
* returns "java.lang.Character$UnicodeBlock"
* byte.class.getName()
* returns "byte"
* (new Object[3]).getClass().getName()
* returns "[Ljava.lang.Object;"
* (new int[3][4][5][6][7][8][9]).getClass().getName()
* returns "[[[[[[[I"
*
* {@code class Shimmer implements FloorWax, DessertTopping { ... }}
*
* suppose the value of {@code s} is an instance of
* {@code Shimmer}; the value of the expression:
*
* {@code s.getClass().getInterfaces()[0]}
*
* is the {@code Class} object that represents interface
* {@code FloorWax}; and the value of:
*
* {@code s.getClass().getInterfaces()[1]}
*
* is the {@code Class} object that represents interface
* {@code DessertTopping}.
*
*
*
* If this {@code Class} object represents a primitive type or
* void, its {@code public}, {@code abstract}, and {@code final}
* modifiers are always {@code true}.
* For {@code Class} objects representing void, primitive types, and
* arrays, the values of other modifiers are {@code false} other
* than as specified above.
*
*
*
* If this {@code Class} object represents a primitive type or
* void, the flags are {@code PUBLIC}, {@code ABSTRACT}, and
* {@code FINAL}.
* For {@code Class} objects representing void, primitive types, and
* arrays, access flags are absent other than as specified above.
*
* @see #getModifiers()
* @jvms 4.1 The ClassFile Structure
* @jvms 4.7.6 The InnerClasses Attribute
* @since 20
*/
public Set
*
*
* The canonical name for a primitive class is the keyword for the
* corresponding primitive type ({@code byte}, {@code short},
* {@code char}, {@code int}, and so on).
*
*
*
*
* @apiNote There may be more than one method with a particular name
* and parameter types in a class because while the Java language forbids a
* class to declare multiple methods with the same signature but different
* return types, the Java virtual machine does not. This
* increased flexibility in the virtual machine can be used to
* implement various language features. For example, covariant
* returns can be implemented with {@linkplain
* java.lang.reflect.Method#isBridge bridge methods}; the bridge
* method and the overriding method would have the same
* signature but different return types.
*
* @return the array of {@code Method} objects representing the
* public methods of this class
*
* @jls 8.2 Class Members
* @jls 8.4 Method Declarations
* @since 1.1
*/
public Method[] getMethods() {
return copyMethods(privateGetPublicMethods());
}
/**
* Returns an array containing {@code Constructor} objects reflecting
* all the public constructors of the class represented by this
* {@code Class} object. An array of length 0 is returned if the
* class has no public constructors, or if the class is an array class, or
* if the class reflects a primitive type or void.
*
* @apiNote
* While this method returns an array of {@code
* Constructor
*
*
*
*
*
*
*
* @apiNote There may be more than one method with matching name and
* parameter types in a class because while the Java language forbids a
* class to declare multiple methods with the same signature but different
* return types, the Java virtual machine does not. This
* increased flexibility in the virtual machine can be used to
* implement various language features. For example, covariant
* returns can be implemented with {@linkplain
* java.lang.reflect.Method#isBridge bridge methods}; the bridge
* method and the overriding method would have the same
* signature but different return types. This method would return the
* overriding method as it would have a more specific return type.
*
* @param name the name of the method
* @param parameterTypes the list of parameters
* @return the {@code Method} object that matches the specified
* {@code name} and {@code parameterTypes}
* @throws NoSuchMethodException if a matching method is not found
* or if the name is {@value ConstantDescs#INIT_NAME} or
* {@value ConstantDescs#CLASS_INIT_NAME}.
* @throws NullPointerException if {@code name} is {@code null}
*
* @jls 8.2 Class Members
* @jls 8.4 Method Declarations
* @since 1.1
*/
public Method getMethod(String name, Class... parameterTypes)
throws NoSuchMethodException {
Objects.requireNonNull(name);
Method method = getMethod0(name, parameterTypes);
if (method == null) {
throw new NoSuchMethodException(methodToString(name, parameterTypes));
}
return getReflectionFactory().copyMethod(method);
}
/**
* Returns a {@code Constructor} object that reflects the specified
* public constructor of the class represented by this {@code Class}
* object. The {@code parameterTypes} parameter is an array of
* {@code Class} objects that identify the constructor's formal
* parameter types, in declared order.
*
* If this {@code Class} object represents an inner class
* declared in a non-static context, the formal parameter types
* include the explicit enclosing instance as the first parameter.
*
*
*
*
*
*
*
* @param name name of the desired resource
* @return A {@link java.io.InputStream} object; {@code null} if no
* resource with this name is found, or the resource is in a package
* that is not {@linkplain Module#isOpen(String, Module) open} to at
* least the caller module.
* @throws NullPointerException If {@code name} is {@code null}
*
* @see Module#getResourceAsStream(String)
* @since 1.1
*/
@CallerSensitive
public InputStream getResourceAsStream(String name) {
name = resolveName(name);
Module thisModule = getModule();
if (thisModule.isNamed()) {
// check if resource can be located by caller
if (Resources.canEncapsulate(name)
&& !isOpenToCaller(name, Reflection.getCallerClass())) {
return null;
}
// resource not encapsulated or in package open to caller
String mn = thisModule.getName();
ClassLoader cl = classLoader;
try {
// special-case built-in class loaders to avoid the
// need for a URL connection
if (cl == null) {
return BootLoader.findResourceAsStream(mn, name);
} else if (cl instanceof BuiltinClassLoader bcl) {
return bcl.findResourceAsStream(mn, name);
} else {
URL url = cl.findResource(mn, name);
return (url != null) ? url.openStream() : null;
}
} catch (IOException | SecurityException e) {
return null;
}
}
// unnamed module
ClassLoader cl = classLoader;
if (cl == null) {
return ClassLoader.getSystemResourceAsStream(name);
} else {
return cl.getResourceAsStream(name);
}
}
/**
* Finds a resource with a given name.
*
* '\u002f'), then the absolute name of the resource is the
* portion of the {@code name} following the {@code '/'}.
*
*
* {@code modified_package_name/name}
*
*
* '\u002e').
*
*
*
*
*
* @param name name of the desired resource
* @return A {@link java.net.URL} object; {@code null} if no resource with
* this name is found, the resource cannot be located by a URL, or the
* resource is in a package that is not
* {@linkplain Module#isOpen(String, Module) open} to at least the caller
* module.
* @throws NullPointerException If {@code name} is {@code null}
* @since 1.1
*/
@CallerSensitive
public URL getResource(String name) {
name = resolveName(name);
Module thisModule = getModule();
if (thisModule.isNamed()) {
// check if resource can be located by caller
if (Resources.canEncapsulate(name)
&& !isOpenToCaller(name, Reflection.getCallerClass())) {
return null;
}
// resource not encapsulated or in package open to caller
String mn = thisModule.getName();
ClassLoader cl = classLoader;
try {
if (cl == null) {
return BootLoader.findResource(mn, name);
} else {
return cl.findResource(mn, name);
}
} catch (IOException ioe) {
return null;
}
}
// unnamed module
ClassLoader cl = classLoader;
if (cl == null) {
return ClassLoader.getSystemResource(name);
} else {
return cl.getResource(name);
}
}
/**
* Returns true if a resource with the given name can be located by the
* given caller. All resources in a module can be located by code in
* the module. For other callers, then the package needs to be open to
* the caller.
*/
private boolean isOpenToCaller(String name, Class caller) {
// assert getModule().isNamed();
Module thisModule = getModule();
Module callerModule = (caller != null) ? caller.getModule() : null;
if (callerModule != thisModule) {
String pn = Resources.toPackageName(name);
if (thisModule.getDescriptor().packages().contains(pn)) {
if (callerModule == null) {
// no caller, return true if the package is open to all modules
return thisModule.isOpen(pn);
}
if (!thisModule.isOpen(pn, callerModule)) {
// package not open to caller
return false;
}
}
}
return true;
}
private transient final ProtectionDomain protectionDomain;
/** Holder for the protection domain returned when the internal domain is null */
private static class Holder {
private static final ProtectionDomain allPermDomain;
static {
Permissions perms = new Permissions();
perms.add(new AllPermission());
allPermDomain = new ProtectionDomain(null, perms);
}
}
/**
* Returns the {@code ProtectionDomain} of this class.
*
* @return the ProtectionDomain of this class
*
* @see java.security.ProtectionDomain
* @since 1.2
*/
public ProtectionDomain getProtectionDomain() {
if (protectionDomain == null) {
return Holder.allPermDomain;
} else {
return protectionDomain;
}
}
/*
* Returns the Class object for the named primitive type. Type parameter T
* avoids redundant casts for trusted code.
*/
static native '\u002f'), then the absolute name of the resource is the
* portion of the {@code name} following the {@code '/'}.
*
*
* {@code modified_package_name/name}
*
*
* '\u002e').
*
*
* {@code TC_CLASS} ClassDescriptor
* A ClassDescriptor is a special cased serialization of
* a {@code java.io.ObjectStreamClass} instance.
*
* A new handle is generated for the initial time the class descriptor
* is written into the stream. Future references to the class descriptor
* are written as references to the initial class descriptor instance.
*
* @see java.io.ObjectStreamClass
*/
@java.io.Serial
private static final ObjectStreamField[] serialPersistentFields =
new ObjectStreamField[0];
/**
* Returns the assertion status that would be assigned to this
* class if it were to be initialized at the time this method is invoked.
* If this class has had its assertion status set, the most recent
* setting will be returned; otherwise, if any package default assertion
* status pertains to this class, the most recent setting for the most
* specific pertinent package default assertion status is returned;
* otherwise, if this class is not a system class (i.e., it has a
* class loader) its class loader's default assertion status is returned;
* otherwise, the system class default assertion status is returned.
*
* @apiNote
* Few programmers will have any need for this method; it is provided
* for the benefit of the JDK itself. (It allows a class to determine at
* the time that it is initialized whether assertions should be enabled.)
* Note that this method is not guaranteed to return the actual
* assertion status that was (or will be) associated with the specified
* class when it was (or will be) initialized.
*
* @return the desired assertion status of the specified class.
* @see java.lang.ClassLoader#setClassAssertionStatus
* @see java.lang.ClassLoader#setPackageAssertionStatus
* @see java.lang.ClassLoader#setDefaultAssertionStatus
* @since 1.4
*/
public boolean desiredAssertionStatus() {
ClassLoader loader = classLoader;
// If the loader is null this is a system class, so ask the VM
if (loader == null)
return desiredAssertionStatus0(this);
// If the classloader has been initialized with the assertion
// directives, ask it. Otherwise, ask the VM.
synchronized(loader.assertionLock) {
if (loader.classAssertionStatus != null) {
return loader.desiredAssertionStatus(getName());
}
}
return desiredAssertionStatus0(this);
}
// Retrieves the desired assertion status of this class from the VM
private static native boolean desiredAssertionStatus0(Class clazz);
/**
* Returns true if and only if this class was declared as an enum in the
* source code.
*
* Note that {@link java.lang.Enum} is not itself an enum class.
*
* Also note that if an enum constant is declared with a class body,
* the class of that enum constant object is an anonymous class
* and not the class of the declaring enum class. The
* {@link Enum#getDeclaringClass} method of an enum constant can
* be used to get the class of the enum class declaring the
* constant.
*
* @return true if and only if this class was declared as an enum in the
* source code
* @since 1.5
* @jls 8.9.1 Enum Constants
*/
public boolean isEnum() {
// An enum must both directly extend java.lang.Enum and have
// the ENUM bit set; classes for specialized enum constants
// don't do the former.
return (this.getModifiers() & ENUM) != 0 &&
this.getSuperclass() == java.lang.Enum.class;
}
/**
* Returns {@code true} if and only if this class is a record class.
*
*
*
*
*
* {@code "L" +} N {@code + "." +
* where N is the {@linkplain ClassLoader##binary-name binary name}
* encoded in internal form indicated by the {@code class} file passed to
* {@link MethodHandles.Lookup#defineHiddenClass(byte[], boolean, MethodHandles.Lookup.ClassOption...)
* Lookup::defineHiddenClass}, and {@code
*
*
*