Exception.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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,
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 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package java.lang;

/**
 * The class {@code Exception} and its subclasses are a form of
 * {@code Throwable} that indicates conditions that a reasonable
 * application might want to catch.
 *
 * <p>The class {@code Exception} and any subclasses that are not also
 * subclasses of {@link RuntimeException} are <em>checked
 * exceptions</em>.  Checked exceptions need to be declared in a
 * method or constructor's {@code throws} clause if they can be thrown
 * by the execution of the method or constructor and propagate outside
 * the method or constructor boundary.
 *
 * @author Frank Yellin
 * @jls 11.2 Compile-Time Checking of Exceptions
 * @see java.lang.Error
 * @since 1.0
 */
/*
 * Java应用层发生的异常
 *
 * 异常体系：
 *                           Throwable
 *                               |
 *                    +----------+-----------+
 *                    |                      |
 *                Exception                Error
 *                    |                      |
 *        +-----------+-----------+         ...
 *        |                       |
 * RuntimeException              ...
 *        |
 *       ...
 *
 * Throwable       : 所有异常的祖先类
 * RuntimeException: 运行时异常，或称非检查异常；这类异常意味着程序出现了难以恢复的错误，允许不进行捕获
 * Exception       : 除运行时异常之外的异常，或称检查异常；这类异常意味着程序出现错误时可能是允许被恢复的，需要在编译期就捕获，否则无法编译
 * Error           : 非常严重的异常，该类异常往往意味着JVM内部出现了问题
 */
public class Exception extends Throwable {
    
    static final long serialVersionUID = -3387516993124229948L;
    
    /**
     * Constructs a new exception with {@code null} as its detail message.
     * The cause is not initialized, and may subsequently be initialized by a
     * call to {@link #initCause}.
     */
    public Exception() {
        super();
    }
    
    /**
     * Constructs a new exception with the specified detail message.  The
     * cause is not initialized, and may subsequently be initialized by
     * a call to {@link #initCause}.
     *
     * @param message the detail message. The detail message is saved for
     *                later retrieval by the {@link #getMessage()} method.
     */
    public Exception(String message) {
        super(message);
    }
    
    /**
     * Constructs a new exception with the specified detail message and
     * cause.  <p>Note that the detail message associated with
     * {@code cause} is <i>not</i> automatically incorporated in
     * this exception's detail message.
     *
     * @param message the detail message (which is saved for later retrieval
     *                by the {@link #getMessage()} method).
     * @param cause   the cause (which is saved for later retrieval by the
     *                {@link #getCause()} method).  (A {@code null} value is
     *                permitted, and indicates that the cause is nonexistent or
     *                unknown.)
     *
     * @since 1.4
     */
    public Exception(String message, Throwable cause) {
        super(message, cause);
    }
    
    /**
     * Constructs a new exception with the specified cause and a detail
     * message of {@code (cause==null ? null : cause.toString())} (which
     * typically contains the class and detail message of {@code cause}).
     * This constructor is useful for exceptions that are little more than
     * wrappers for other throwables (for example, {@link
     * java.security.PrivilegedActionException}).
     *
     * @param cause the cause (which is saved for later retrieval by the
     *              {@link #getCause()} method).  (A {@code null} value is
     *              permitted, and indicates that the cause is nonexistent or
     *              unknown.)
     *
     * @since 1.4
     */
    public Exception(Throwable cause) {
        super(cause);
    }
    
    /**
     * Constructs a new exception with the specified detail message,
     * cause, suppression enabled or disabled, and writable stack
     * trace enabled or disabled.
     *
     * @param message            the detail message.
     * @param cause              the cause.  (A {@code null} value is permitted,
     *                           and indicates that the cause is nonexistent or unknown.)
     * @param enableSuppression  whether or not suppression is enabled
     *                           or disabled
     * @param writableStackTrace whether or not the stack trace should
     *                           be writable
     *
     * @since 1.7
     */
    protected Exception(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
        super(message, cause, enableSuppression, writableStackTrace);
    }
}