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Closeables.java
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Thu, May 9, 22:49

Closeables.java
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/*
* Copyright (C) 2007 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.io;
import com.google.common.annotations.Beta;
import com.google.common.annotations.VisibleForTesting;
import java.io.Closeable;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.Nullable;
/**
* Utility methods for working with {@link Closeable} objects.
*
* @author Michael Lancaster
* @since 1.0
*/
@Beta
public final class Closeables {
@VisibleForTesting static final Logger logger
= Logger.getLogger(Closeables.class.getName());
private Closeables() {}
/**
* Closes a {@link Closeable}, with control over whether an
* {@code IOException} may be thrown. This is primarily useful in a
* finally block, where a thrown exception needs to be logged but not
* propagated (otherwise the original exception will be lost).
*
* <p>If {@code swallowIOException} is true then we never throw
* {@code IOException} but merely log it.
*
* <p>Example:
*
* <p><pre>public void useStreamNicely() throws IOException {
* SomeStream stream = new SomeStream("foo");
* boolean threw = true;
* try {
* // Some code which does something with the Stream. May throw a
* // Throwable.
* threw = false; // No throwable thrown.
* } finally {
* // Close the stream.
* // If an exception occurs, only rethrow it if (threw==false).
* Closeables.close(stream, threw);
* }
* </pre>
*
* @param closeable the {@code Closeable} object to be closed, or null,
* in which case this method does nothing
* @param swallowIOException if true, don't propagate IO exceptions
* thrown by the {@code close} methods
* @throws IOException if {@code swallowIOException} is false and
* {@code close} throws an {@code IOException}.
*/
public static void close(@Nullable Closeable closeable,
boolean swallowIOException) throws IOException {
if (closeable == null) {
return;
}
try {
closeable.close();
} catch (IOException e) {
if (swallowIOException) {
logger.log(Level.WARNING,
"IOException thrown while closing Closeable.", e);
} else {
throw e;
}
}
}
/**
* Equivalent to calling {@code close(closeable, true)}, but with no
* IOException in the signature.
* @param closeable the {@code Closeable} object to be closed, or null, in
* which case this method does nothing
*/
public static void closeQuietly(@Nullable Closeable closeable) {
try {
close(closeable, true);
} catch (IOException e) {
logger.log(Level.SEVERE, "IOException should not have been thrown.", e);
}
}
}

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