stream-->流的输入和输出

package stream.demo1;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;

public class TransferTo
{
    
    /**
     * 相对于ChannelCopy，该方法具有更好的效率
     */
    public static void main(String[] args)
        throws IOException
    {
        if (args.length != 2)
        {
            System.out.println("arguments : sourcefile destfile");
            System.exit(1);
        }
        FileChannel in = new FileInputStream(args[0]).getChannel();
        FileChannel out = new FileOutputStream(args[1]).getChannel();
        // 把输入流和输出流相连，在数据的读取和写入时可以考虑这个
        in.transferTo(0, in.size(), out);// or out.transferFrom(in, 0, in.size());
        
    }
    
}

 

package stream.demo1;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class ChannelCopy
{
    private static final int BSIZE = 1024;
    
    public static void main(String[] args)
        throws Exception
    {
        if (args.length != 2)
        {
            System.out.println("arguments : siyrcefuke destfuke");
            System.exit(1);
        }
        FileChannel in = new FileInputStream(args[0]).getChannel();
        FileChannel out = new FileOutputStream(args[1]).getChannel();
        ByteBuffer buffer = ByteBuffer.allocate(BSIZE);
        while (in.read(buffer) != -1)
        {
            buffer.flip();
            out.write(buffer);
            buffer.clear();
        }
    }
}

 

package stream.demo1;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class GetChannel
{
    private static final int BSIZE = 1024;
    
    public static void main(String[] args)
        throws Exception
    {
        // FileChannel用于读取、写入、映射和操作文件的通道。
        FileChannel fc = new FileOutputStream("data.txt").getChannel();
        
        fc.write(ByteBuffer.wrap("Some more".getBytes()));// ByteBuffer.wrap("Some more".getBytes()) 将字节数组包装到缓冲区中。
        fc.close();
        // RandomAccessFile文件操作类,RandomAccessFile是一个很特殊的IO操作类,对文件可以既可以读，也可以写，甚至可以跳过一些数据进行操作
        fc = new RandomAccessFile("data.txt", "rw").getChannel();
        fc.position(fc.size());// 把指针移动fc.size的距离进行数据操作
        fc.write(ByteBuffer.wrap("Some more".getBytes()));
        fc.close();
        fc = new FileInputStream("data.txt").getChannel();
        // ByteBuffer.allocate(BSIZE) 分配一个新的字节缓冲区
        ByteBuffer buffer = ByteBuffer.allocate(BSIZE);
        fc.read(buffer);
        
        buffer.flip();
        while (buffer.hasRemaining())
            System.out.print((char)buffer.get());
    }
}