Java example source code file (Basic.java)

This example Java source code file (Basic.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

exception, extendedfileinputstream, extendedfileoutputstream, fileinputstream, filenotfoundexception, fileoutputstream, iterations, nio, nullpointerexception, readablebytechannel, runtimeexception, string, test, writablebytechannel

The Basic.java Java example source code

/*
 * Copyright (c) 2001, 2008, 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 4417152 4481572 6248930 6725399 6884800
 * @summary Test Channels basic functionality
 */

import java.io.*;
import java.nio.*;
import java.nio.charset.*;
import java.nio.channels.*;


public class Basic {

    static String message;

    static String encoding;

    static File blah;

    static int ITERATIONS = 500;

    public static void main(String[] args) throws Exception {
        message = "ascii data for a test";
        encoding = "ISO-8859-1";
        test();
        message = "\ucafe\ubabe\ucafe\ubabe\ucafe\ubabe";
        encoding = "UTF-8";
        test();
    }

    static void failNpeExpected() {
        throw new RuntimeException("Did not get the expected NullPointerException.");
    }

    private static void test() throws Exception {
        //Test if methods of Channels throw NPE with null argument(s)
        try {
            Channels.newInputStream((ReadableByteChannel)null);
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            Channels.newOutputStream((WritableByteChannel)null);
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            ReadableByteChannel channel = Channels.newChannel((InputStream)null);
            failNpeExpected();
        } catch (NullPointerException ne) {}  // OK. As expected.

        try {
            WritableByteChannel channel = Channels.newChannel((OutputStream)null);
            failNpeExpected();
        } catch (NullPointerException ne) {}  // OK. As expected.

        WritableByteChannel wbc = new WritableByteChannel() {
            public int write(ByteBuffer src) { return 0; }
            public void close() throws IOException { }
            public boolean isOpen() { return true; }
        };

        ReadableByteChannel rbc = new ReadableByteChannel() {
            public int read(ByteBuffer dst) { return 0; }
            public void close() {}
            public boolean isOpen() { return true; }
        };

        try {
            Channels.newReader((ReadableByteChannel)null,
                               Charset.defaultCharset().newDecoder(),
                               -1);
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            Channels.newReader(rbc, (CharsetDecoder)null, -1);
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            Channels.newReader((ReadableByteChannel)null,
                               Charset.defaultCharset().name());
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            Channels.newReader(rbc, null);
            failNpeExpected();
        } catch (NullPointerException npe) {}


        try {
            Channels.newReader(null, null);
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            Channels.newWriter((WritableByteChannel)null,
                               Charset.defaultCharset().newEncoder(),
                               -1);
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            Channels.newWriter(null, null, -1);
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            Channels.newWriter(wbc, null, -1);
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            Channels.newWriter((WritableByteChannel)null,
                               Charset.defaultCharset().name());
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            Channels.newWriter(wbc, null);
            failNpeExpected();
        } catch (NullPointerException npe) {}

        try {
            Channels.newWriter(null, null);
            failNpeExpected();
        } catch (NullPointerException npe) {}


        try {
            blah = File.createTempFile("blah", null);

            testNewOutputStream(blah);
            readAndCheck(blah);
            blah.delete();

            writeOut(blah, ITERATIONS);
            testNewInputStream(blah);
            blah.delete();

            testNewChannelOut(blah);
            readAndCheck(blah);
            blah.delete();

            writeOut(blah, ITERATIONS);
            testNewChannelIn(blah);
            test4481572(blah);
            blah.delete();

            testNewWriter(blah);
            readAndCheck(blah);
            blah.delete();

            writeOut(blah, ITERATIONS);
            testNewReader(blah);

        } finally {
            blah.delete();
        }
    }

    private static void readAndCheck(File blah) throws Exception {
        FileInputStream fis = new FileInputStream(blah);
        int messageSize = message.length() * ITERATIONS * 3 + 1;
        byte bb[] = new byte[messageSize];
        int bytesRead = 0;
        int totalRead = 0;
        while (bytesRead != -1) {
            totalRead += bytesRead;
            bytesRead = fis.read(bb, totalRead, messageSize - totalRead);
        }
        String result = new String(bb, 0, totalRead, encoding);
        int len = message.length();
        for (int i=0; i<ITERATIONS; i++) {
            String segment = result.substring(i++ * len, i * len);
            if (!segment.equals(message))
                throw new RuntimeException("Test failed");
        }
        fis.close();
    }

    private static void writeOut(File blah, int limit) throws Exception {
        FileOutputStream fos = new FileOutputStream(blah);
        for (int i=0; i<limit; i++)
            fos.write(message.getBytes(encoding));
        fos.close();
    }

    private static void testNewOutputStream(File blah) throws Exception {
        FileOutputStream fos = new FileOutputStream(blah);
        FileChannel fc = fos.getChannel();
        WritableByteChannel wbc = (WritableByteChannel)fc;
        OutputStream os = Channels.newOutputStream(wbc);
        for (int i=0; i<ITERATIONS; i++)
            os.write(message.getBytes(encoding));
        os.close();
        fos.close();
    }

    private static void testNewInputStream(File blah) throws Exception {
        FileInputStream fis = new FileInputStream(blah);
        FileChannel fc = fis.getChannel();
        InputStream is = Channels.newInputStream(fc);
        int messageSize = message.length() * ITERATIONS * 3 + 1;
        byte bb[] = new byte[messageSize];

        int bytesRead = 0;
        int totalRead = 0;
        while (bytesRead != -1) {
            totalRead += bytesRead;
            long rem = Math.min(fc.size() - totalRead, (long)Integer.MAX_VALUE);
            if (is.available() != (int)rem)
                throw new RuntimeException("available not useful or not maximally useful");
            bytesRead = is.read(bb, totalRead, messageSize - totalRead);
        }
        if (is.available() != 0)
           throw new RuntimeException("available() should return 0 at EOF");

        String result = new String(bb, 0, totalRead, encoding);
        int len = message.length();
        for (int i=0; i<ITERATIONS; i++) {
            String segment = result.substring(i++ * len, i * len);
            if (!segment.equals(message))
                throw new RuntimeException("Test failed");
        }
        is.close();
        fis.close();
    }

    private static void testNewChannelOut(File blah) throws Exception {
        ExtendedFileOutputStream fos = new ExtendedFileOutputStream(blah);
        WritableByteChannel wbc = Channels.newChannel(fos);
        for (int i=0; i<ITERATIONS; i++)
            wbc.write(ByteBuffer.wrap(message.getBytes(encoding)));
        wbc.close();
        fos.close();
    }

    private static void testNewChannelIn(File blah) throws Exception {
        ExtendedFileInputStream fis = new ExtendedFileInputStream(blah);
        ReadableByteChannel rbc = Channels.newChannel(fis);

        int messageSize = message.length() * ITERATIONS * 3;
        byte data[] = new byte[messageSize+1];
        ByteBuffer bb = ByteBuffer.wrap(data);

        int bytesRead = 0;
        int totalRead = 0;
        while (bytesRead != -1) {
            totalRead += bytesRead;
            bytesRead = rbc.read(bb);
        }

        String result = new String(data, 0, totalRead, encoding);
        int len = message.length();
        for (int i=0; i<ITERATIONS; i++) {
            String segment = result.substring(i++ * len, i * len);
            if (!segment.equals(message))
                throw new RuntimeException("Test failed");
        }
        rbc.close();
        fis.close();
    }

    // Causes BufferOverflowException if bug 4481572 is present.
    private static void test4481572(File blah) throws Exception {
        ExtendedFileInputStream fis = new ExtendedFileInputStream(blah);
        ReadableByteChannel rbc = Channels.newChannel(fis);

        byte data[] = new byte[9000];
        ByteBuffer bb = ByteBuffer.wrap(data);

        int bytesRead = 1;
        int totalRead = 0;
        while (bytesRead > 0) {
            totalRead += bytesRead;
            bytesRead = rbc.read(bb);
        }
        rbc.close();
        fis.close();
    }

    private static void testNewWriter(File blah) throws Exception {
        FileOutputStream fos = new FileOutputStream(blah);
        WritableByteChannel wbc = (WritableByteChannel)fos.getChannel();
        Writer w = Channels.newWriter(wbc, encoding);
        char data[] = new char[40];
        message.getChars(0, message.length(), data, 0);
        for (int i=0; i<ITERATIONS; i++)
            w.write(data, 0, message.length());
        w.flush();
        w.close();
        fos.close();
    }

    private static void testNewReader(File blah) throws Exception {
        FileInputStream fis = new FileInputStream(blah);
        ReadableByteChannel rbc = (ReadableByteChannel)fis.getChannel();
        Reader r = Channels.newReader(rbc, encoding);

        int messageSize = message.length() * ITERATIONS;
        char data[] = new char[messageSize];

        int totalRead = 0;
        int charsRead = 0;
        while (totalRead < messageSize) {
            totalRead += charsRead;
            charsRead = r.read(data, totalRead, messageSize - totalRead);
        }
        String result = new String(data, 0, totalRead);
        int len = message.length();
        for (int i=0; i<ITERATIONS; i++) {
            String segment = result.substring(i++ * len, i * len);
            if (!segment.equals(message))
                throw new RuntimeException("Test failed");
        }
        r.close();
        fis.close();
    }
}

class ExtendedFileInputStream extends java.io.FileInputStream {
    ExtendedFileInputStream(File file) throws FileNotFoundException {
        super(file);
    }
}

class ExtendedFileOutputStream extends java.io.FileOutputStream {
    ExtendedFileOutputStream(File file) throws FileNotFoundException {
        super(file);
    }
}