100 lines
4.6 KiB
Java
100 lines
4.6 KiB
Java
/*
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* Copyright (c) 2009, 2021, 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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* An object that may hold resources (such as file or socket handles)
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* until it is closed. The {@link #close()} method of an {@code AutoCloseable}
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* object is called automatically when exiting a {@code
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* try}-with-resources block for which the object has been declared in
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* the resource specification header. This construction ensures prompt
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* release, avoiding resource exhaustion exceptions and errors that
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* may otherwise occur.
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*
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* @apiNote
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* <p>It is possible, and in fact common, for a base class to
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* implement AutoCloseable even though not all of its subclasses or
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* instances will hold releasable resources. For code that must operate
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* in complete generality, or when it is known that the {@code AutoCloseable}
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* instance requires resource release, it is recommended to use {@code
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* try}-with-resources constructions. However, when using facilities such as
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* {@link java.util.stream.Stream} that support both I/O-based and
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* non-I/O-based forms, {@code try}-with-resources blocks are in
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* general unnecessary when using non-I/O-based forms.
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*
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* @author Josh Bloch
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* @since 1.7
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*/
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public interface AutoCloseable {
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/**
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* Closes this resource, relinquishing any underlying resources.
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* This method is invoked automatically on objects managed by the
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* {@code try}-with-resources statement.
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*
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* @apiNote
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* While this interface method is declared to throw {@code
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* Exception}, implementers are <em>strongly</em> encouraged to
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* declare concrete implementations of the {@code close} method to
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* throw more specific exceptions, or to throw no exception at all
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* if the close operation cannot fail.
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*
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* <p> Cases where the close operation may fail require careful
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* attention by implementers. It is strongly advised to relinquish
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* the underlying resources and to internally <em>mark</em> the
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* resource as closed, prior to throwing the exception. The {@code
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* close} method is unlikely to be invoked more than once and so
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* this ensures that the resources are released in a timely manner.
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* Furthermore it reduces problems that could arise when the resource
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* wraps, or is wrapped, by another resource.
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*
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* <p><em>Implementers of this interface are also strongly advised
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* to not have the {@code close} method throw {@link
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* InterruptedException}.</em>
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*
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* This exception interacts with a thread's interrupted status,
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* and runtime misbehavior is likely to occur if an {@code
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* InterruptedException} is {@linkplain Throwable#addSuppressed
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* suppressed}.
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*
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* More generally, if it would cause problems for an
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* exception to be suppressed, the {@code AutoCloseable.close}
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* method should not throw it.
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*
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* <p>Note that unlike the {@link java.io.Closeable#close close}
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* method of {@link java.io.Closeable}, this {@code close} method
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* is <em>not</em> required to be idempotent. In other words,
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* calling this {@code close} method more than once may have some
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* visible side effect, unlike {@code Closeable.close} which is
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* required to have no effect if called more than once.
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*
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* However, implementers of this interface are strongly encouraged
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* to make their {@code close} methods idempotent.
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*
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* @throws Exception if this resource cannot be closed
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*/
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void close() throws Exception;
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}
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