Update #0 - First Release

sources/main/java/com/google/common/io/Closeables.java

@@ -0,0 +1,143 @@
+/*
+ * 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.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;
+
+import com.google.common.annotations.Beta;
+import com.google.common.annotations.VisibleForTesting;
+
+/**
+ * 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);
+		}
+	}
+}