CustomAutoCloseableSample.java

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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
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 * 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;
 
public class CustomAutoCloseableSample {
 
    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);
        }
    }
 
    public static class TeeStream extends OutputStream {
 
        private final OutputStream fileStream;
        private final OutputStream outputStream;
 
        public TeeStream(OutputStream outputStream, Path outputFile) throws IOException {
            this.fileStream = new BufferedOutputStream(Files.newOutputStream(outputFile));
            this.outputStream = outputStream;
        }
 
        @Override
        public void write(int b) throws IOException {
            fileStream.write(b);
            outputStream.write(b);
        }
 
        @Override
        public void flush() throws IOException {
            outputStream.flush();
            fileStream.flush();
        }
 
        @Override
        public void close() throws IOException {
            try (OutputStream file = fileStream) {
                flush();
            }
        }
    }
}