Java example source code file (Position.java)

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Java - Java tags/keywords

append, bufferedwriter, charset, filechannel, ioexception, iso8859_1, nio, path, position, random, read, runtimeexception, string, util

The Position.java Java example source code

/*
 * Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/* @test
 * @bug 4429043 6526860
 * @summary Test position method of FileChannel
 */

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.*;
import static java.nio.file.StandardOpenOption.*;
import java.nio.charset.Charset;
import java.util.Random;


/**
 * Testing FileChannel's position method.
 */

public class Position {

    private static final Charset ISO8859_1 = Charset.forName("8859_1");

    private static final Random generator = new Random();

    public static void main(String[] args) throws Exception {
        Path blah = Files.createTempFile("blah", null);
        blah.toFile().deleteOnExit();
        initTestFile(blah);

        for (int i=0; i<10; i++) {
            try (FileChannel fc = (generator.nextBoolean()) ?
                    FileChannel.open(blah, READ) :
                    new FileInputStream(blah.toFile()).getChannel()) {
                for (int j=0; j<100; j++) {
                    long newPos = generator.nextInt(1000);
                    fc.position(newPos);
                    if (fc.position() != newPos)
                        throw new RuntimeException("Position failed");
                }
            }
        }

        for (int i=0; i<10; i++) {
            try (FileChannel fc = (generator.nextBoolean()) ?
                     FileChannel.open(blah, APPEND) :
                     new FileOutputStream(blah.toFile(), true).getChannel()) {
                for (int j=0; j<10; j++) {
                    if (fc.position() != fc.size())
                        throw new RuntimeException("Position expected to be size");
                    byte[] buf = new byte[generator.nextInt(100)];
                    fc.write(ByteBuffer.wrap(buf));
                }
            }
        }

        Files.delete(blah);
    }

    /**
     * Creates file blah:
     * 0000
     * 0001
     * 0002
     * 0003
     * .
     * .
     * .
     * 3999
     *
     */
    private static void initTestFile(Path blah) throws IOException {
        try (BufferedWriter awriter = Files.newBufferedWriter(blah, ISO8859_1)) {
            for(int i=0; i<4000; i++) {
                String number = new Integer(i).toString();
                for (int h=0; h<4-number.length(); h++)
                    awriter.write("0");
                awriter.write(""+i);
                awriter.newLine();
            }
        }
    }
}