How to use java Channel

1. Description

Channel is an object through which data can be read and written. It can be viewed as a stream in IO. But compared with streams, it has some differences:

Channel is bidirectional and can be read or written, while streams are one-way.

Channel can be read and written asynchronously.

Channel reading and writing must go through the buffer object.

2. Example

Use channels and indirect buffers to complete.

FileInputStream fis=null;           //引用
FileOutputStream fout=null;
FileChannel channel=null;  //通道引用
FileChannel outchannel=null;
try {
fis = new FileInputStream("sb.jpg");     //源文件
fout = new FileOutputStream("bb.jpg");  //目标文件   
channel = fis.getChannel();             //获取连接源文件的通道
outchannel = fout.getChannel();         //获取连接目标文件的通道
//指定缓冲区 非直接缓冲区
ByteBuffer buffer=ByteBuffer.allocate(1024);  //创建缓冲区 用来传输数据
while(channel.read(buffer)!=-1)          //从连接源文件的管道读取数据到缓冲区
{
//将缓冲区反转
buffer.flip();
outchannel.write(buffer);        //将缓冲区中的数据写入连接到目标文件的管道
buffer.clear();                  //"清空"缓冲区
}

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