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+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of Oracle nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * This source code is provided to illustrate the usage of a given feature
+ * or technique and has been deliberately simplified. Additional steps
+ * required for a production-quality application, such as security checks,
+ * input validation, and proper error handling, might not be present in
+ * this sample code.
+ */
+
+import java.io.BufferedOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.PrintStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+/**
+ * This sample demonstrates the ability to create custom resource that
+ * implements the {@code AutoCloseable} interface. This resource can be used in
+ * the try-with-resources construct.
+ */
+public class CustomAutoCloseableSample {
+
+ /**
+ * The main method for the CustomAutoCloseableSample program.
+ *
+ * @param args is not used.
+ */
+ public static void main(String[] args) {
+ /*
+ * TeeStream will be closed automatically after the try block.
+ */
+ try (TeeStream teeStream = new TeeStream(System.out, Paths.get("out.txt"));
+ PrintStream out = new PrintStream(teeStream)) {
+ out.print("Hello, world");
+ } catch (Exception e) {
+ e.printStackTrace();
+ System.exit(1);
+ }
+ }
+
+ /**
+ * Passes the output through to the specified output stream while copying it into a file.
+ * The TeeStream functionality is similar to the Unix tee utility.
+ * TeeStream implements AutoCloseable interface. See OutputStream for details.
+ */
+ public static class TeeStream extends OutputStream {
+
+ private final OutputStream fileStream;
+ private final OutputStream outputStream;
+
+ /**
+ * Creates a TeeStream.
+ *
+ * @param outputStream an output stream.
+ * @param outputFile an path to file.
+ * @throws IOException If an I/O error occurs.
+ */
+ public TeeStream(OutputStream outputStream, Path outputFile) throws IOException {
+ this.fileStream = new BufferedOutputStream(Files.newOutputStream(outputFile));
+ this.outputStream = outputStream;
+ }
+
+ /**
+ * Writes the specified byte to the specified output stream
+ * and copies it to the file.
+ *
+ * @param b the byte to be written.
+ * @throws IOException If an I/O error occurs.
+ */
+ @Override
+ public void write(int b) throws IOException {
+ fileStream.write(b);
+ outputStream.write(b);
+ }
+
+ /**
+ * Flushes this output stream and forces any buffered output bytes
+ * to be written out.
+ * The <code>flush</code> method of <code>TeeStream</code> flushes
+ * the specified output stream and the file output stream.
+ *
+ * @throws IOException if an I/O error occurs.
+ */
+ @Override
+ public void flush() throws IOException {
+ outputStream.flush();
+ fileStream.flush();
+ }
+
+ /**
+ * Closes underlying streams and resources.
+ * The external output stream won't be closed.
+ * This method is the member of AutoCloseable interface and
+ * it will be invoked automatically after the try-with-resources block.
+ *
+ * @throws IOException If an I/O error occurs.
+ */
+ @Override
+ public void close() throws IOException {
+ try (OutputStream file = fileStream) {
+ flush();
+ }
+ }
+ }
+}