code: /*
   * 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);
      }
    }
  }