/*

 * Copyright (c) 1994, 2019, 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.annotation.Annotation;

import java.lang.constant.ClassDesc;

import java.lang.invoke.TypeDescriptor;

import java.lang.module.ModuleReader;

import java.lang.ref.SoftReference;

import java.io.IOException;

import java.io.InputStream;

import java.io.ObjectStreamField;

import java.lang.reflect.AnnotatedElement;

import java.lang.reflect.AnnotatedType;

import java.lang.reflect.Array;

import java.lang.reflect.Constructor;

import java.lang.reflect.Executable;

import java.lang.reflect.Field;

import java.lang.reflect.GenericArrayType;

import java.lang.reflect.GenericDeclaration;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Member;

import java.lang.reflect.Method;

import java.lang.reflect.Modifier;

import java.lang.reflect.Proxy;

import java.lang.reflect.Type;

import java.lang.reflect.TypeVariable;

import java.lang.constant.Constable;

import java.net.URL;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collection;

import java.util.HashMap;

import java.util.LinkedHashMap;

import java.util.LinkedHashSet;

import java.util.List;

import java.util.Map;

import java.util.Objects;

import java.util.Optional;

import java.util.StringJoiner;

import java.util.stream.Stream;

import java.util.stream.Collectors;

import jdk.internal.HotSpotIntrinsicCandidate;

import jdk.internal.loader.BootLoader;

import jdk.internal.loader.BuiltinClassLoader;

import jdk.internal.misc.Unsafe;

import jdk.internal.module.Resources;

import jdk.internal.reflect.CallerSensitive;

import jdk.internal.reflect.ConstantPool;

import jdk.internal.reflect.Reflection;

import jdk.internal.reflect.ReflectionFactory;

import jdk.internal.vm.annotation.ForceInline;

import sun.invoke.util.Wrapper;

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 sun.reflect.annotation.*;

import sun.reflect.misc.ReflectUtil;

/**

 * Instances of the class {@code Class} represent classes and interfaces

 * in a running Java application. An enum type is a kind of class and an

 * annotation type 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 a {@code Class}

 * object is constructed automatically by the Java Virtual Machine

 * when a class loader invokes one of the

 * {@link ClassLoader#defineClass(String,byte[], int,int) defineClass} methods

 * and passes the bytes of a {@code class} file.

 *

 * <p> 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. A few

 * characteristics are determined by the class loading environment at run time,

 * such as the module returned by {@link #getModule() getModule()}.

 *

 * <p> Some methods of class {@code Class} expose whether the declaration of

 * a class or interface in Java source code was <em>enclosed</em> within

 * another declaration. Other methods describe how a class or interface

 * is situated in a <em>nest</em>. A <a id="nest">nest</a> 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 <em>nestmates</em>.

 * One nestmate acts as the

 * <em>nest host</em>, 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.

 *

 * <p> The following example uses a {@code Class} object to print the

 * class name of an object:

 *

 * <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:

 *

 * <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   1.0

 */

public final class Class<T> implements java.io.Serializable,

                              GenericDeclaration,

                              Type,

                              AnnotatedElement,

                              TypeDescriptor.OfField<Class<?>>,

                              Constable {

    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();

    }

    /*

     * Private constructor. Only the Java Virtual Machine creates Class objects.

     * This constructor is not used and prevents the default constructor being

     * generated.

     */

    private Class(ClassLoader loader, Class<?> arrayComponentType) {

        // Initialize final field for classLoader.  The initialization value of non-null

        // prevents future JIT optimizations from assuming this final field is null.

        classLoader = loader;

        componentType = arrayComponentType;

    }

    /**

     * 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". If this {@code Class} object represents an array type,

     * this method returns "class " followed by {@code getName}.

     *

     * @return a string representation of this class object.

     */

    public String toString() {

        return (isInterface() ? "interface " : (isPrimitive() ? "" : "class "))

            + getName();

    }

    /**

     * Returns a string describing this {@code Class}, including

     * information about modifiers and type parameters.

     *

     * The string is formatted as a list of type modifiers, if any,

     * followed by the kind of type (empty string for primitive types

     * and {@code class}, {@code enum}, {@code interface}, or

     * <code>&#64;</code>{@code interface}, as appropriate), followed

     * by the type's name, followed by an angle-bracketed

     * comma-separated list of the type's type parameters, if any,

     * including informative bounds on the type parameters, if any.

     *

     * A space is used to separate modifiers from one another and to

     * separate any modifiers from the kind of type. The modifiers

     * occur in canonical order. If there are no type parameters, the

     * type parameter list is elided.

     *

     * For an array type, the string starts with the type name,

     * followed by an angle-bracketed comma-separated list of the

     * type's type parameters, if any, followed by a sequence of

     * {@code []} characters, one set of brackets per dimension of

     * the array.

     *

     * <p>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(' ');

                }

                if (isAnnotation()) {

                    sb.append('@');

                }

                if (isInterface()) { // Note: all annotation types are interfaces

                    sb.append("interface");

                } else {

                    if (isEnum())

                        sb.append("enum");

                    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();

        }

    }

    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:

     *

     * <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.

     * @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 forName0(className, true, ClassLoader.getClassLoader(caller), caller);

    }

    /**

     * 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 and load 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.

     *

     * @param name       fully qualified name of the desired class

     * @param initialize if {@code true} the class will be initialized (which implies linking).

     *                   See Section 12.4 of <em>The Java Language Specification</em>.

     * @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

     * @throws    SecurityException

     *            if a security manager is present, and the {@code loader} is

     *            {@code null}, and the caller's class loader is not

     *            {@code null}, and the caller does not have the

     *            {@link RuntimePermission}{@code ("getClassLoader")}

     *

     * @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

     * @since     1.2

     */

    @CallerSensitive

    public static Class<?> forName(String name, boolean initialize,

                                   ClassLoader loader)

        throws ClassNotFoundException

    {

        Class<?> caller = null;

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            // Reflective call to get caller class is only needed if a security manager

            // is present.  Avoid the overhead of making this call otherwise.

            caller = Reflection.getCallerClass();

            if (loader == null) {

                ClassLoader ccl = ClassLoader.getClassLoader(caller);

                if (ccl != null) {

                    sm.checkPermission(

                        SecurityConstants.GET_CLASSLOADER_PERMISSION);

                }

            }

        }

        return forName0(name, initialize, loader, caller);

    }

    /** 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 <a href="ClassLoader.html#binary-name">

     * binary name</a> in the given module.

     *

     * <p> 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}. </p>

     *

     * <p> 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. </p>

     *

     * <p> This method does not check whether the requested class is

     * accessible to its caller. </p>

     *

     * @apiNote

     * This method returns {@code null} on failure rather than

     * throwing a {@link ClassNotFoundException}, as is done by

     * the {@link #forName(String, boolean, ClassLoader)} method.

     * The security check is a stack-based permission check if the caller

     * loads a class in another module.

     *

     * @param  module   A module

     * @param  name     The <a href="ClassLoader.html#binary-name">binary name</a>

     *                  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

     *

     * @throws SecurityException

     *         <ul>

     *         <li> if the caller is not the specified module and

     *         {@code RuntimePermission("getClassLoader")} permission is denied; or</li>

     *         <li> access to the module content is denied. For example,

     *         permission check will be performed when a class loader calls

     *         {@link ModuleReader#open(String)} to read the bytes of a class file

     *         in a module.</li>

     *         </ul>

     *

     * @jls 12.2 Loading of Classes and Interfaces

     * @jls 12.3 Linking of Classes and Interfaces

     * @since 9

     * @spec JPMS

     */

    @CallerSensitive

    public static Class<?> forName(Module module, String name) {

        Objects.requireNonNull(module);

        Objects.requireNonNull(name);

        ClassLoader cl;

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            Class<?> caller = Reflection.getCallerClass();

            if (caller != null && caller.getModule() != module) {

                // if caller is null, Class.forName is the last java frame on the stack.

                // java.base has all permissions

                sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);

            }

            PrivilegedAction<ClassLoader> pa = module::getClassLoader;

            cl = AccessController.doPrivileged(pa);

        } else {

            cl = module.getClassLoader();

        }