136 lines
4.8 KiB
Java
136 lines
4.8 KiB
Java
/*
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* Copyright (c) 1994, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.lang;
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/**
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* Thrown when an application attempts to use {@code null} in a
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* case where an object is required. These include:
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* <ul>
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* <li>Calling the instance method of a {@code null} object.
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* <li>Accessing or modifying the field of a {@code null} object.
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* <li>Taking the length of {@code null} as if it were an array.
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* <li>Accessing or modifying the slots of {@code null} as if it
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* were an array.
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* <li>Throwing {@code null} as if it were a {@code Throwable}
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* value.
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* </ul>
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* <p>
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* Applications should throw instances of this class to indicate
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* other illegal uses of the {@code null} object.
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*
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* {@code NullPointerException} objects may be constructed by the
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* virtual machine as if {@linkplain Throwable#Throwable(String,
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* Throwable, boolean, boolean) suppression were disabled and/or the
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* stack trace was not writable}.
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*
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* @since 1.0
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*/
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public class NullPointerException extends RuntimeException {
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@java.io.Serial
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private static final long serialVersionUID = 5162710183389028792L;
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/**
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* Constructs a {@code NullPointerException} with no detail message.
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*/
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public NullPointerException() {
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super();
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}
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/**
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* Constructs a {@code NullPointerException} with the specified
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* detail message.
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*
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* @param s the detail message.
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*/
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public NullPointerException(String s) {
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super(s);
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}
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// BEGIN Android-removed: no extended NPEs in Android.
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/*
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// 0: no backtrace filled in, no message computed.
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// 1: backtrace filled in, no message computed.
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// 2: message computed
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private transient int extendedMessageState;
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private transient String extendedMessage;
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/**
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* {@inheritDoc}
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*
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public synchronized Throwable fillInStackTrace() {
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// If the stack trace is changed the extended NPE algorithm
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// will compute a wrong message. So compute it beforehand.
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if (extendedMessageState == 0) {
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extendedMessageState = 1;
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} else if (extendedMessageState == 1) {
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extendedMessage = getExtendedNPEMessage();
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extendedMessageState = 2;
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}
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return super.fillInStackTrace();
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}
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/**
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* Returns the detail message string of this throwable.
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*
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* <p> If a non-null message was supplied in a constructor it is
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* returned. Otherwise, an implementation specific message or
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* {@code null} is returned.
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*
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* @implNote
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* If no explicit message was passed to the constructor, and as
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* long as certain internal information is available, a verbose
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* description of the null reference is returned.
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* The internal information is not available in deserialized
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* NullPointerExceptions.
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*
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* @return the detail message string, which may be {@code null}.
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*
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public String getMessage() {
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String message = super.getMessage();
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if (message == null) {
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synchronized(this) {
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if (extendedMessageState == 1) {
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// Only the original stack trace was filled in. Message will
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// compute correctly.
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extendedMessage = getExtendedNPEMessage();
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extendedMessageState = 2;
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}
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return extendedMessage;
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}
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}
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return message;
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}
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/**
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* Get an extended exception message. This returns a string describing
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* the location and cause of the exception. It returns null for
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* exceptions where this is not applicable.
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*
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private native String getExtendedNPEMessage();
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*/
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// END Android-removed: no extended NPEs in Android.
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}
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