/src/share/classes/java/lang/Class.java

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/*
 * Copyright (c) 1994, 2010, 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.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.Member;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Constructor;
import java.lang.reflect.Modifier;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.InvocationTargetException;
import java.lang.ref.SoftReference;
import java.io.InputStream;
import java.io.ObjectStreamField;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.Map;
import java.util.HashMap;
import sun.misc.Unsafe;
import sun.reflect.ConstantPool;
import sun.reflect.Reflection;
import sun.reflect.ReflectionFactory;
import sun.reflect.generics.factory.CoreReflectionFactory;
import sun.reflect.generics.factory.GenericsFactory;
import sun.reflect.generics.repository.ClassRepository;
import sun.reflect.generics.repository.MethodRepository;
import sun.reflect.generics.repository.ConstructorRepository;
import sun.reflect.generics.scope.ClassScope;
import sun.security.util.SecurityConstants;
import java.lang.annotation.Annotation;
import sun.reflect.annotation.*;

/**
 * Instances of the class {@code Class} represent classes and
 * interfaces in a running Java application.  An enum is a kind of
 * class and an annotation is a kind of interface.  Every array also
 * belongs to a class that is reflected as a {@code Class} object
 * that is shared by all arrays with the same element type and number
 * of dimensions.  The primitive Java types ({@code boolean},
 * {@code byte}, {@code char}, {@code short},
 * {@code int}, {@code long}, {@code float}, and
 * {@code double}), and the keyword {@code void} are also
 * represented as {@code Class} objects.
 *
 * <p> {@code Class} has no public constructor. Instead {@code Class}
 * objects are constructed automatically by the Java Virtual Machine as classes
 * are loaded and by calls to the {@code defineClass} method in the class
 * loader.
 *
 * <p> The following example uses a {@code Class} object to print the
 * class name of an object:
 *
 * <p> <blockquote><pre>
 *     void printClassName(Object obj) {
 *         System.out.println("The class of " + obj +
 *                            " is " + obj.getClass().getName());
 *     }
 * </pre></blockquote>
 *
 * <p> It is also possible to get the {@code Class} object for a named
 * type (or for void) using a class literal.  See Section 15.8.2 of
 * <cite>The Java&trade; Language Specification</cite>.
 * For example:
 *
 * <p> <blockquote>
 *     {@code System.out.println("The name of class Foo is: "+Foo.class.getName());}
 * </blockquote>
 *
 * @param <T> the type of the class modeled by this {@code Class}
 * object.  For example, the type of {@code String.class} is {@code
 * Class<String>}.  Use {@code Class<?>} if the class being modeled is
 * unknown.
 *
 * @author  unascribed
 * @see     java.lang.ClassLoader#defineClass(byte[], int, int)
 * @since   JDK1.0
 */
public final
    class Class<T> implements java.io.Serializable,
                              java.lang.reflect.GenericDeclaration,
                              java.lang.reflect.Type,
                              java.lang.reflect.AnnotatedElement {
    private static final int ANNOTATION= 0x00002000;
    private static final int ENUM      = 0x00004000;
    private static final int SYNTHETIC = 0x00001000;

    private static native void registerNatives();
    static {
        registerNatives();
    }

    /*
     * Constructor. Only the Java Virtual Machine creates Class
     * objects.
     */
    private Class() {}


    /**
     * Converts the object to a string. The string representation is the
     * string "class" or "interface", followed by a space, and then by the
     * fully qualified name of the class in the format returned by
     * {@code getName}.  If this {@code Class} object represents a
     * primitive type, this method returns the name of the primitive type.  If
     * this {@code Class} object represents void this method returns
     * "void".
     *
     * @return a string representation of this class object.
     */
    public String toString() {
        return (isInterface() ? "interface " : (isPrimitive() ? "" : "class "))
            + getName();
    }


    /**
     * Returns the {@code Class} object associated with the class or
     * interface with the given string name.  Invoking this method is
     * equivalent to:
     *
     * <blockquote>
     *  {@code Class.forName(className, true, currentLoader)}
     * </blockquote>
     *
     * where {@code currentLoader} denotes the defining class loader of
     * the current class.
     *
     * <p> For example, the following code fragment returns the
     * runtime {@code Class} descriptor for the class named
     * {@code java.lang.Thread}:
     *
     * <blockquote>
     *   {@code Class t = Class.forName("java.lang.Thread")}
     * </blockquote>
     * <p>
     * A call to {@code forName("X")} causes the class named
     * {@code X} to be initialized.
     *
     * @param      className   the fully qualified name of the desired class.
     * @return     the {@code Class} object for the class with the
     *             specified name.
     * @exception LinkageError if the linkage fails
     * @exception ExceptionInInitializerError if the initialization provoked
     *            by this method fails
     * @exception ClassNotFoundException if the class cannot be located
     */
    public static Class<?> forName(String className)
                throws ClassNotFoundException {
        return forName0(className, true, ClassLoader.getCallerClassLoader());
    }


    /**
     * Returns the {@code Class} object associated with the class or
     * interface with the given string name, using the given class loader.
     * Given the fully qualified name for a class or interface (in the same
     * format returned by {@code getName}) this method attempts to
     * locate, load, and link the class or interface.  The specified class
     * loader is used to load the class or interface.  If the parameter
     * {@code loader} is 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.
     *
     * <p> If {@code name} denotes a primitive type or void, an attempt
     * will be made to locate a user-defined class in the unnamed package whose
     * name is {@code name}. Therefore, this method cannot be used to
     * obtain any of the {@code Class} objects representing primitive
     * types or void.
     *
     * <p> If {@code name} denotes an array class, the component type of
     * the array class is loaded but not initialized.
     *
     * <p> For example, in an instance method the expression:
     *
     * <blockquote>
     *  {@code Class.forName("Foo")}
     * </blockquote>
     *
     * is equivalent to:
     *
     * <blockquote>
     *  {@code Class.forName("Foo", true, this.getClass().getClassLoader())}
     * </blockquote>
     *
     * Note that this method throws errors related to loading, linking or
     * initializing as specified in Sections 12.2, 12.3 and 12.4 of <em>The
     * Java Language Specification</em>.
     * Note that this method does not check whether the requested class
     * is accessible to its caller.
     *
     * <p> If the {@code loader} is {@code null}, and a security
     * manager is present, and the caller's class loader is not null, then this
     * method calls the security manager's {@code checkPermission} method
     * with a {@code RuntimePermission("getClassLoader")} permission to
     * ensure it's ok to access the bootstrap class loader.
     *
     * @param name       fully qualified name of the desired class
     * @param initialize whether the class must be initialized
     * @param loader     class loader from which the class must be loaded
     * @return           class object representing the desired class
     *
     * @exception LinkageError if the linkage fails
     * @exception ExceptionInInitializerError if the initialization provoked
     *            by this method fails
     * @exception ClassNotFoundException if the class cannot be located by
     *            the specified class loader
     *
     * @see       java.lang.Class#forName(String)
     * @see       java.lang.ClassLoader
     * @since     1.2
     */
    public static Class<?> forName(String name, boolean initialize,
                                   ClassLoader loader)
        throws ClassNotFoundException
    {
        if (loader == null) {
            SecurityManager sm = System.getSecurityManager();
            if (sm != null) {
                ClassLoader ccl = ClassLoader.getCallerClassLoader();
                if (ccl != null) {
                    sm.checkPermission(
                        SecurityConstants.GET_CLASSLOADER_PERMISSION);
                }
            }
        }
        return forName0(name, initialize, loader);
    }

    /** Called after security checks have been made. */
    private static native Class<?> forName0(String name, boolean initialize,
                                            ClassLoader loader)
        throws ClassNotFoundException;

    /**
     * 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.
     *
     * <p>Note that 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}.
     *
     * @return     a newly allocated instance of the class represented by this
     *             object.
     * @exception  IllegalAccessException  if the class or its nullary
     *               constructor is not accessible.
     * @exception  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.
     * @exception  ExceptionInInitializerError if the initialization
     *               provoked by this method fails.
     * @exception  SecurityException
     *             If a security manager, <i>s</i>, is present and any of the
     *             following conditions is met:
     *
     *             <ul>
     *
     *             <li> invocation of
     *             {@link SecurityManager#checkMemberAccess
     *             s.checkMemberAccess(this, Member.PUBLIC)} denies
     *             creation of new instances of this class
     *
     *             <li> the caller's class loader is not the same as or an
     *             ancestor of the class loader for the current class and
     *             invocation of {@link SecurityManager#checkPackageAccess
     *             s.checkPackageAccess()} denies access to the package
     *             of this class
     *
     *             </ul>
     *
     */
    public T newInstance()
        throws InstantiationException, IllegalAccessException
    {
        if (System.getSecurityManager() != null) {
            checkMemberAccess(Member.PUBLIC, ClassLoader.getCallerClassLoader());
        }
        return newInstance0();
    }

    private T newInstance0()
        throws InstantiationException, IllegalAccessException
    {
        // NOTE: the following code may not be strictly correct under
        // the current Java memory model.

        // Constructor lookup
        if (cachedConstructor == null) {
            if (this == Class.class) {
                throw new IllegalAccessException(
                    "Can not call newInstance() on the Class for java.lang.Class"
                );
            }
            try {
                Class<?>[] empty = {};
                final Constructor<T> c = getConstructor0(empty, Member.DECLARED);
                // Disable accessibility checks on the constructor
                // since we have to do the security check here anyway
                // (the stack depth is wrong for the Constructor's
                // security check to work)
                java.security.AccessController.doPrivileged(
                    new java.security.PrivilegedAction<Void>() {
                        public Void run() {
                                c.setAccessible(true);
                                return null;
                            }
                        });
                cachedConstructor = c;
            } catch (NoSuchMethodException e) {
                throw (InstantiationException)
                    new InstantiationException(getName()).initCause(e);
            }
        }
        Constructor<T> tmpConstructor = cachedConstructor;
        // Security check (same as in java.lang.reflect.Constructor)
        int modifiers = tmpConstructor.getModifiers();
        if (!Reflection.quickCheckMemberAccess(this, modifiers)) {
            Class<?> caller = Reflection.getCallerClass(3);
            if (newInstanceCallerCache != caller) {
                Reflection.ensureMemberAccess(caller, this, null, modifiers);
                newInstanceCallerCache = caller;
            }
        }
        // Run constructor
        try {
            return tmpConstructor.newInstance((Object[])null);
        } catch (InvocationTargetException e) {
            Unsafe.getUnsafe().throwException(e.getTargetException());
            // Not reached
            return null;
        }
    }
    private volatile transient Constructor<T> cachedConstructor;
    private volatile transient Class<?>       newInstanceCallerCache;


    /**
     * Determines if the specified {@code Object} is assignment-compatible
     * with the object represented by this {@code Class}.  This method is
     * the dynamic equivalent of the Java language {@code instanceof}
     * operator. The method returns {@code true} if the specified
     * {@code Object} argument is non-null and can be cast to the
     * reference type represented by this {@code Class} object without
     * raising a {@code ClassCastException.} It returns {@code false}
     * otherwise.
     *
     * <p> 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 JDK1.1
     */
    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}.
     *
     * <p> 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 <em>The Java Language
     * Specification</em>, sections 5.1.1 and 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
     * @exception NullPointerException if the specified Class parameter is
     *            null.
     * @since JDK1.1
     */
    public native boolean isAssignableFrom(Class<?> cls);


    /**
     * Determines if the specified {@code Class} object represents an
     * interface type.
     *
     * @return  {@code true} if this object represents an interface;
     *          {@code false} otherwise.
     */
    public native boolean isInterface();


    /**
     * Determines if this {@code Class} object represents an array class.
     *
     * @return  {@code true} if this object represents an array class;
     *          {@code false} otherwise.
     * @since   JDK1.1
     */
    public native boolean isArray();


    /**
     * Determines if the specified {@code Class} object represents a
     * primitive type.
     *
     * <p> 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 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}.
     *
     * <p> These objects may only be accessed via the following public static
     * final variables, and are the only {@code Class} objects for which
     * this method returns {@code true}.
     *
     * @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 JDK1.1
     */
    public native boolean isPrimitive();

    /**
     * Returns true if this {@code Class} object represents an annotation
     * type.  Note that if this method returns true, {@link #isInterface()}
     * would also return true, as all annotation types are also interfaces.
     *
     * @return {@code true} if this class object represents an annotation
     *      type; {@code false} otherwise
     * @since 1.5
     */
    public boolean isAnnotation() {
        return (getModifiers() & ANNOTATION) != 0;
    }

    /**
     * Returns {@code true} if this class is a synthetic class;
     * returns {@code false} otherwise.
     * @return {@code true} if and only if this class is a synthetic class as
     *         defined by the Java Language Specification.
     * @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,
     * as a {@code String}.
     *
     * <p> If this class object represents a reference type that is not an
     * array type then the binary name of the class is returned, as specified
     * by
     * <cite>The Java&trade; Language Specification</cite>.
     *
     * <p> If this class object represents a primitive type or void, then the
     * name returned is a {@code String} equal to the Java language
     * keyword corresponding to the primitive type or void.
     *
     * <p> If this class object represents a class of arrays, then the internal
     * form of the name consists of the name of the element type preceded by
     * one or more '{@code [}' characters representing the depth of the array
     * nesting.  The encoding of element type names is as follows:
     *
     * <blockquote><table summary="Element types and encodings">
     * <tr><th> Element Type <th> &nbsp;&nbsp;&nbsp; <th> Encoding
     * <tr><td> boolean      <td> &nbsp;&nbsp;&nbsp; <td align=center> Z
     * <tr><td> byte         <td> &nbsp;&nbsp;&nbsp; <td align=center> B
     * <tr><td> char         <td> &nbsp;&nbsp;&nbsp; <td align=center> C
     * <tr><td> class or interface
     *                       <td> &nbsp;&nbsp;&nbsp; <td align=center> L<i>classname</i>;
     * <tr><td> double       <td> &nbsp;&nbsp;&nbsp; <td align=center> D
     * <tr><td> float        <td> &nbsp;&nbsp;&nbsp; <td align=center> F
     * <tr><td> int          <td> &nbsp;&nbsp;&nbsp; <td align=center> I
     * <tr><td> long         <td> &nbsp;&nbsp;&nbsp; <td align=center> J
     * <tr><td> short        <td> &nbsp;&nbsp;&nbsp; <td align=center> S
     * </table></blockquote>
     *
     * <p> The class or interface name <i>classname</i> is the binary name of
     * the class specified above.
     *
     * <p> Examples:
     * <blockquote><pre>
     * String.class.getName()
     *     returns "java.lang.String"
     * 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"
     * </pre></blockquote>
     *
     * @return  the name of the class or interface
     *          represented by this object.
     */
    public String getName() {
        String name = this.name;
        if (name == null)
            this.name = name = getName0();
        return name;
    }

    // cache the name to reduce the number of calls into the VM
    private transient String name;
    private native String getName0();

    /**
     * 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.
     *
     * <p> If a security manager is present, and the caller's class loader is
     * not null and the caller's class loader is not the same as or an ancestor of
     * the class loader for the class whose class loader is requested, then
     * this method calls the security manager's {@code checkPermission}
     * method with a {@code RuntimePermission("getClassLoader")}
     * permission to ensure it's ok to access the class loader for the class.
     *
     * <p>If this object
     * represents a primitive type or void, null is returned.
     *
     * @return  the class loader that loaded the class or interface
     *          represented by this object.
     * @throws SecurityException
     *    if a security manager exists and its
     *    {@code checkPermission} method denies
     *    access to the class loader for the class.
     * @see java.lang.ClassLoader
     * @see SecurityManager#checkPermission
     * @see java.lang.RuntimePermission
     */
    public ClassLoader getClassLoader() {
        ClassLoader cl = getClassLoader0();
        if (cl == null)
            return null;
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            ClassLoader ccl = ClassLoader.getCallerClassLoader();
            if (ccl != null && ccl != cl && !cl.isAncestor(ccl)) {
                sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
            }
        }
        return cl;
    }

    // Package-private to allow ClassLoader access
    native ClassLoader getClassLoader0();


    /**
     * 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
     *     <cite>The Java&trade; Virtual Machine Specification</cite>
     * @since 1.5
     */
    @SuppressWarnings("unchecked")
    public TypeVariable<Class<T>>[] getTypeParameters() {
        if (getGenericSignature() != null)
            return (TypeVariable<Class<T>>[])getGenericInfo().getTypeParameters();
        else
            return (TypeVariable<Class<T>>[])new TypeVariable<?>[0];
    }


    /**
     * Returns the {@code Class} representing the superclass of the entity
     * (class, interface, primitive type or void) represented by this
     * {@code Class}.  If this {@code Class} represents either the
     * {@code Object} class, an interface, a primitive type, or void, then
     * null is returned.  If this object represents an array class then the
     * {@code Class} object representing the {@code Object} class is
     * returned.
     *
     * @return the superclass of the class represented by this object.
     */
    public native Class<? super T> getSuperclass();


    /**
     * Returns the {@code Type} representing the direct superclass of
     * the entity (class, interface, primitive type or void) represented by
     * this {@code Class}.
     *
     * <p>If the superclass is a parameterized type, the {@code Type}
     * object returned must accurately reflect the actual type
     * parameters 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} represents either the {@code Object}
     * class, an interface, a primitive type, or void, then null is
     * returned.  If this 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
     *     <cite>The Java&trade; Virtual Machine Specification</cite>
     * @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 superclass of the class represented by this object
     * @since 1.5
     */
    public Type getGenericSuperclass() {
        if (getGenericSignature() != null) {
            // Historical irregularity:
            // Generic signature marks interfaces with superclass = Object
            // but this API returns null for interfaces
            if (isInterface())
                return null;
            return getGenericInfo().getSuperclass();
        } else
            return getSuperclass();
    }

    /**
     * Gets the package for this class.  The class loader of this class is used
     * to find the package.  If the class was loaded by the bootstrap class
     * loader the set of packages loaded from CLASSPATH is searched to find the
     * package of the class. Null is returned if no package object was created
     * by the class loader of this class.
     *
     * <p> Packages have attributes for versions and specifications only if the
     * information was defined in the manifests that accompany the classes, and
     * if the class loader created the package instance with the attributes
     * from the manifest.
     *
     * @return the package of the class, or null if no package
     *         information is available from the archive or codebase.
     */
    public Package getPackage() {
        return Package.getPackage(this);
    }


    /**
     * Determines the interfaces implemented by the class or interface
     * represented by this object.
     *
     * <p> If this object represents a class, the return value is an array
     * containing objects representing all interfaces 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 object. For
     * example, given the declaration:
     * <blockquote>
     * {@code class Shimmer implements FloorWax, DessertTopping { ... }}
     * </blockquote>
     * suppose the value of {@code s} is an instance of
     * {@code Shimmer}; the value of the expression:
     * <blockquote>
     * {@code s.getClass().getInterfaces()[0]}
     * </blockquote>
     * is the {@code Class} object that represents interface
     * {@code FloorWax}; and the value of:
     * <blockquote>
     * {@code s.getClass().getInterfaces()[1]}
     * </blockquote>
     * is the {@code Class} object that represents interface
     * {@code DessertTopping}.
     *
     * <p> If this object represents an interface, the array contains objects
     * representing all interfaces 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 object.
     *
     * <p> If this object represents a class or interface that implements no
     * interfaces, the method returns an array of length 0.
     *
     * <p> If this object represents a primitive type or void, the method
     * returns an array of length 0.
     *
     * @return an array of interfaces implemented by this class.
     */
    public native Class<?>[] getInterfaces();

    /**
     * Returns the {@code Type}s representing the interfaces
     * directly implemented by the class or interface represented by
     * this object.
     *
     * <p>If a superinterface is a parameterized type, the
     * {@code Type} object returned for it must accurately reflect
     * the actual type parameters 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.
     *
     * <p> If this object represents a class, the return value is an
     * array containing objects representing all interfaces
     * 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 object.  In the case of an array class, the
     * interfaces {@code Cloneable} and {@code Serializable} are
     * returned in that order.
     *
     * <p>If this 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 object.
     *
     * <p>If this object represents a class or interface that
     * implements no interfaces, the method returns an array of length
     * 0.
     *
     * <p>If this object represents a primitive type or void, the
     * method returns an array of length 0.
     *
     * @throws java.lang.reflect.GenericSignatureFormatError
     *     if the generic class signature does not conform to the format
     *     specified in
     *     <cite>The Java&trade; Virtual Machine Specification</cite>
     * @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 implemented by this class
     * @since 1.5
     */
    public Type[] getGenericInterfaces() {
        if (getGenericSignature() != null)
            return getGenericInfo().getSuperInterfaces();
        else
            return getInterfaces();
    }


    /**
     * 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 JDK1.1
     */
    public native Class<?> getComponentType();


    /**
     * 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}.
     *
     * <p> If the underlying class is an array class, then its
     * {@code public}, {@code private} and {@code protected}
     * modifiers are the same as those of its component type.  If this
     * {@code Class} represents a primitive type or void, its
     * {@code public} modifier is always {@code true}, and its
     * {@code protected} and {@code private} modifiers are always
     * {@code false}. If this object represents an array class, a
     * primitive type or void, then its {@code final} modifier is always
     * {@code true} and its interface modifier is always
     * {@code false}. The values of its other modifiers are not determined
     * by this specification.
     *
     * <p> The modifier encodings are defined in <em>The Java Virtual Machine
     * Specification</em>, table 4.1.
     *
     * @return the {@code int} representing the modifiers for this class
     * @see     java.lang.reflect.Modifier
     * @since JDK1.1
     */
    public native int getModifiers();


    /**
     * Gets the signers of this class.
     *
     * @return  the signers of this class, or null if there are no signers.  In
     *          particular, this method returns null if this object represents
     *          a primitive type or void.
     * @since   JDK1.1
     */
    public native Object[] getSigners();


    /**
     * Set the signers of this class.
     */
    native void setSigners(Object[] signers);


    /**
     * If this {@code Class} object represents a local or anonymous
     * class within a method, returns a {@link
     * java.lang.reflect.Method Method} object representing the
     * immediately enclosing method of the underlying class. Returns
     * {@code null} otherwise.
     *
     * In particular, this method returns {@code null} if the underlying
     * class is a local or anonymous class immediately enclosed by a type
     * declaration, instance initializer or static initializer.
     *
     * @return the immediately enclosing method of the underlying class, if
     *     that class is a local or anonymous class; otherwise {@code null}.
     * @since 1.5
     */
    public Method getEnclosingMethod() {
        EnclosingMethodInfo enclosingInfo = getEnclosingMethodInfo();

        if (enclosingInfo == null)
            return null;
        else {
            if (!enclosingInfo.isMethod())
                return null;

            MethodRepository typeInfo = MethodRepository.make(enclosingInfo.getDescriptor(),
                                                              getFactory());
            Class<?>   returnType       = toClass(typeInfo.getReturnType());
            Type []    parameterTypes   = typeInfo.getParameterTypes();
            Class<?>[] parameterClasses = new Class<?>[parameterTypes.length];

            // Convert Types to Classes; returned types *should*
            // be class objects since the methodDescriptor's used
            // don't have generics information
            for(int i = 0; i < parameterClasses.length; i++)
                parameterClasses[i] = toClass(parameterTypes[i]);

            /*
             * Loop over all declared methods; match method name,
             * number of and type of parameters, *and* return
             * type.  Matching return type is also necessary
             * because of covariant returns, etc.
             */
            for(Method m: enclosingInfo.getEnclosingClass().getDeclaredMethods()) {
                if (m.getName().equals(enclosingInfo.getName()) ) {
                    Class<?>[] candidateParamClasses = m.getParameterTypes();
                    if (candidateParamClasses.length == parameterClasses.length) {
                        boolean matches = true;
                        for(int i = 0; i < candidateParamClasses.length; i++) {
                            if (!candidateParamClasses[i].equals(parameterClasses[i])) {
                                matches = false;
                                break;
                            }
                        }

                        if (matches) { // finally, check return type
                            if (m.getReturnType().equals(returnType) )
                                return m;
                        }
                    }
                }
            }

            throw new InternalError("Enclosing method not found");
        }
    }

    private native Object[] getEnclosingMethod0();

    private EnclosingMethodInfo getEnclosingMethodInfo() {
        Object[] enclosingInfo = getEnclosingMethod0();
        if (enclosingInfo == null)
            return null;
        else {
            return new EnclosingMethodInfo(enclosingInfo);
        }
    }

    private final static class EnclosingMethodInfo {
        private Class<?> enclosingClass;
        private String name;
        private String descriptor;

        private EnclosingMethodInfo(Object[] enclosingInfo) {
            if (enclosingInfo.length != 3)
                throw new InternalError("Malformed enclosing method information");
            try {
                // The array is expected to have three elements:

                // the immediately enclosing class
                enclosingClass = (Class<?>) enclosingInfo[0];
                assert(enclosingClass != null);

                // the immediately enclosing method or constructor's
                // name (can be null).
                name            = (String)   enclosingInfo[1];

                // the immediately enclosing method or constructor's
                // descriptor (null iff name is).
                descriptor      = (String)   enclosingInfo[2];
                assert((name != null && descriptor != null) || name == descriptor);
            } catch (ClassCastException cce) {
                throw new InternalError("Invalid type in enclosing method information", cce);
            }
        }

        boolean isPartial() {
            return enclosingClass == null || name == null || descriptor == null;
        }

        boolean isConstructor() { return !isPartial() && "<init>".equals(name); }

        boolean isMethod() { return !isPartial() && !isConstructor() && !"<clinit>".equals(name); }

        Class<?> getEnclosingClass() { return enclosingClass; }

        String getName() { return name; }

        String getDescriptor() { return descriptor; }

    }

    private static Class<?> toClass(Type o) {
        if (o instanceof GenericArrayType)
            return Array.newInstance(toClass(((GenericArrayType)o).getGenericComponentType()),
                                     0)
                .getClass();
        return (Class<?>)o;
     }

    /**
     * If this {@code Class} object represents a local or anonymous
     * class within a constructor, returns a {@link
     * java.lang.reflect.Constructor Constructor} object representing
     * the immediately enclosing constructor of the underlying
     * class. Returns {@code null} otherwise.  In particular, this
     * method returns {@code null} if the underlying class is a local
     * or anonymous class immediately enclosed by a type declaration,
     * instance initializer or static initializer.
     *
     * @return the immediately enclosing constructor of the underlying class, if
     *     that class is a local or anonymous class; otherwise {@code null}.
     * @since 1.5
     */
    public Constructor<?> getEnclosingConstructor() {
        EnclosingMethodInfo enclosingInfo = getEnclosingMethodInfo();

        if (enclosingInfo == null)
            return null;
        else {
            if (!enclosingInfo.isConstructor())
                return null;

            ConstructorRepository typeInfo = ConstructorRepository.make(enclosingInfo.getDescriptor(),
                                                                        getFactory());
            Type []    parameterTypes   = typeInfo.getParameterTypes();
            Class<?>[] parameterClasses = new Class<?>[parameterTypes.length];

            // Convert Types to Classes; returned types *should*
            // be class objects since the methodDescriptor's used
            // don't have generics information
            for(int i = 0; i < parameterClasses.length; i++)
                parameterClasses[i] = toClass(parameterTypes[i]);

            /*
             * Loop over all declared constructors; match number
             * of and type of parameters.
             */
            for(Constructor<?> c: enclosingInfo.getEnclosingClass().getDeclaredConstructors()) {
                Class<?>[] candidateParamClasses = c.getParameterTypes();
                if (candidateParamClasses.length == parameterClasses.length) {
                    boolean matches = true;
                    for(int i = 0; i < candidateParamClasses.length; i++) {
                        if (!candidateParamClasses[i].equals(parameterClasses[i])) {
                            matches = false;
                            break;
                        }
                    }

                    if (matches)
                        return c;
                }
            }

            throw new InternalError("Enclosing constructor not found");
        }
    }


    /**
     * If the class or interface represented by this {@code Class} object
     * is a member of another class, returns the {@code Class} object
     * representing the class in which it was declared.  This method returns
     * null if this class or interface is not a member of any other class.  If
     * this {@code Class} object represents an array class, a primitive
     * type, or void,then this method returns null.
     *
     * @return the declaring class for this class
     * @since JDK1.1
     */
    public native Class<?> getDeclaringClass();


    /**
     * Returns the immediately enclosing class of the underlying
     * class.  If the underlying class is a top level class this
     * method returns {@code null}.
     * @return the immediately enclosing class of the underlying class
     * @since 1.5
     */
    public Class<?> getEnclosingClass() {
        // There are five kinds of classes (or interfaces):
        // a) Top level classes
        // b) Nested classes (static member classes)
        // c) Inner classes (non-static member classes)
        // d) Local classes (named classes declared within a method)
        // e) Anonymous classes


        // JVM Spec 4.8.6: A class must have an EnclosingMethod
        // attribute if and only if it is a local class or an
        // anonymous class.
        EnclosingMethodInfo enclosingInfo = getEnclosingMethodInfo();

        if (enclosingInfo == null) {
            // This is a top level or a nested class or an inner class (a, b, or c)
            return getDeclaringClass();
        } else {
            Class<?> enclosingClass = enclosingInfo.getEnclosingClass();
            // This is a local class or an anonymous class (d or e)
            if (enclosingClass == this || enclosingClass == null)
                throw new InternalError("Malformed enclosing method information");
            else
                return enclosingClass;
        }
    }

    /**
     * Returns the simple name of the underlying class as given in the
     * source code. Returns an empty string if the underlying class is
     * anonymous.
     *
     * <p>The simple name of an array is the simple name of the
     * component type with "[]" appended.  In particular the simple
     * name of an array whose component type is anonymous is "[]".
     *
     * @return the simple name of the underlying class
     * @since 1.5
     */
    public String getSimpleName() {
        if (isArray())
            return getComponentType().getSimpleName()+"[]";

        String simpleName = getSimpleBinaryName();
        if (simpleName == null) { // top level class
            simpleName = getName();
            return simpleName.substring(simpleName.lastIndexOf(".")+1); // strip the package name
        }
        // According to JLS3 "Binary Compatibility" (13.1) the binary
        // name of non-package classes (not top level) is the binary
        // name of the immediately enclosing class followed by a '$' followed by:
        // (for nested and inner classes): the simple name.
        // (for local classes): 1 or more digits followed by the simple name.
        // (for anonymous classes): 1 or more digits.

        // Since getSimpleBinaryName() will strip the binary name of
        // the immediatly enclosing class, we are now looking at a
        // string that matches the regular expression "\$[0-9]*"
        // followed by a simple name (considering the simple of an
        // anonymous class to be the empty string).

        // Remove leading "\$[0-9]*" from the name
        int length = simpleName.length();
        if (length < 1 || simpleName.charAt(0) != '$')
            throw new InternalError("Malformed class name");
        int index = 1;
        while (index < length && isAsciiDigit(simpleName.charAt(index)))
            index++;
        // Eventually, this is the empty string iff this is an anonymous class
        return simpleName.substring(index);
    }

    /**
     * Character.isDigit answers {@code true} to some non-ascii
     * digits.  This one does not.
     */
    private static boolean isAsciiDigit(char c) {
        return '0' <= c && c <= '9';
    }

    /**
     * Returns the canonical name of the underlying class as
     * defined by the Java Language Specification.  Returns null if
     * the underlying class does not have a canonical name (i.e., if
     * it is a local or anonymous class or an array whose component
     * type does not have a canonical name).
     * @return the canonical name of the underlying class if it exists, and
     * {@code null} otherwise.
     * @since 1.5
     */
    public String getCanonicalName() {
        if (isArray()) {
            String canonicalName = getComponentType().getCanonicalName();
            if (canonicalName != null)
                return canonicalName + "[]";
            else
                return null;
        }
        if (isLocalOrAnonymousClass())
            return null;
        Class<?> enclosingClass = getEnclosingClass();
        if (enclosingClass == null) { // top level class
            return getName();
        } else {
  …

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