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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 java.io.Reader;
 
Utility methods for working with java.io.Closeable objects.

Author(s):
Michael Lancaster
Since:
1.0
 
 public final class Closeables {
   @VisibleForTesting static final Logger logger
       = Logger.getLogger(Closeables.class.getName());
 
   private Closeables() {}

  
Closes a java.io.Closeable, with control over whether an 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).

If swallowIOException is true then we never throw IOException but merely log it.

Example:

   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);
     }
   }}

Parameters:
closeable the Closeable object to be closed, or null, in which case this method does nothing
swallowIOException if true, don't propagate IO exceptions thrown by the close methods
Throws:
java.io.IOException if swallowIOException is false and close throws an IOException.
 
   public static void close(@Nullable Closeable closeable,
       boolean swallowIOExceptionthrows IOException {
     if (closeable == null) {
       return;
     }
     try {
       closeable.close();
     } catch (IOException e) {
       if (swallowIOException) {
         .log(.,
             "IOException thrown while closing Closeable."e);
       } else {
         throw e;
       }
     }
   }

  
Closes the given java.io.InputStream, logging any IOException that's thrown rather than propagating it.

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 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.

Parameters:
inputStream the input stream to be closed, or null in which case this method does nothing
Since:
17.0
  public static void closeQuietly(@Nullable InputStream inputStream) {
    try {
      close(inputStreamtrue);
    } catch (IOException impossible) {
      throw new AssertionError(impossible);
    }
  }

  
Closes the given java.io.Reader, logging any IOException that's thrown rather than propagating it.

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 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.

Parameters:
reader the reader to be closed, or null in which case this method does nothing
Since:
17.0
  public static void closeQuietly(@Nullable Reader reader) {
    try {
      close(readertrue);
    } catch (IOException impossible) {
      throw new AssertionError(impossible);
    }
  }
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