com.google.common.io.Closeables.java Source code

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Here is the source code for com.google.common.io.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.io.InputStream;
import java.io.Reader;
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: <pre>   {@code
     *
     *   public void useStreamNicely() throws IOException {
     *     SomeStream stream = new SomeStream("foo");
     *     boolean threw = true;
     *     try {
     *       // ... code which does something with the stream ...
     *       threw = false;
     *     } finally {
     *       // If an exception occurs, rethrow it only 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;
            }
        }
    }

    /**
     * Closes the given {@link InputStream}, logging any {@code IOException} that's thrown rather
     * than propagating it.
     *
     * <p>While it's not safe in the general case to ignore exceptions that are thrown when closing
     * an I/O resource, it should generally be safe in the case of a resource that's being used only
     * for reading, such as an {@code InputStream}. Unlike with writable resources, there's no
     * chance that a failure that occurs when closing the stream indicates a meaningful problem such
     * as a failure to flush all bytes to the underlying resource.
     *
     * @param inputStream the input stream to be closed, or {@code null} in which case this method
     *     does nothing
     * @since 17.0
     */
    public static void closeQuietly(@Nullable InputStream inputStream) {
        try {
            close(inputStream, true);
        } catch (IOException impossible) {
            throw new AssertionError(impossible);
        }
    }

    /**
     * Closes the given {@link Reader}, logging any {@code IOException} that's thrown rather than
     * propagating it.
     *
     * <p>While it's not safe in the general case to ignore exceptions that are thrown when closing
     * an I/O resource, it should generally be safe in the case of a resource that's being used only
     * for reading, such as a {@code Reader}. Unlike with writable resources, there's no chance that
     * a failure that occurs when closing the reader indicates a meaningful problem such as a failure
     * to flush all bytes to the underlying resource.
     *
     * @param reader the reader to be closed, or {@code null} in which case this method does nothing
     * @since 17.0
     */
    public static void closeQuietly(@Nullable Reader reader) {
        try {
            close(reader, true);
        } catch (IOException impossible) {
            throw new AssertionError(impossible);
        }
    }
}