Main.java Source code

Introduction

Here is the source code for Main.java

Source

/*
 * Copyright (c) 2004 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 3nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose,
 * including teaching and use in open-source projects.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book, 
 * please visit http://www.davidflanagan.com/javaexamples3.
 */
//package je3.nio;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;

public class Main {
    public static void main(String[] args) throws IOException {
        // Open file streams and get channels for them.
        ReadableByteChannel in = new FileInputStream(args[0]).getChannel();
        WritableByteChannel out;
        if (args.length > 1)
            out = new FileOutputStream(args[1]).getChannel();
        else
            out = Channels.newChannel(System.out);

        // Do the copy
        copy(in, out);

        // Exception handling and stream-closing code has been omitted.
    }

    // Read all available bytes from one channel and copy them to the other.
    public static void copy(ReadableByteChannel in, WritableByteChannel out) throws IOException {
        // First, we need a buffer to hold blocks of copied bytes.
        ByteBuffer buffer = ByteBuffer.allocateDirect(32 * 1024);

        // Now loop until no more bytes to read and the buffer is empty
        while (in.read(buffer) != -1 || buffer.position() > 0) {
            // The read() call leaves the buffer in "fill mode". To prepare
            // to write bytes from the bufferwe have to put it in "drain mode"
            // by flipping it: setting limit to position and position to zero
            buffer.flip();

            // Now write some or all of the bytes out to the output channel
            out.write(buffer);

            // Compact the buffer by discarding bytes that were written,
            // and shifting any remaining bytes. This method also
            // prepares the buffer for the next call to read() by setting the
            // position to the limit and the limit to the buffer capacity.
            buffer.compact();
        }
    }
}