1-NIO使用

Posted 2021-01-25 da-peng

1.FileChannel 和 Buffer

package nio._Buffer;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class Demo {
    public static void main(String[] args) throws IOException {
        RandomAccessFile aFile = new RandomAccessFile("f:/zhuopeng/nioFile.txt","rw");
        FileChannel fileChannel = aFile.getChannel();


        RandomAccessFile aFile2 = new RandomAccessFile("f:/zhuopeng/nioFile2.txt","rw");
        FileChannel fileChannel2 = aFile2.getChannel();

        //分配内存，创建一个buffer，capacity为48
        ByteBuffer buf = ByteBuffer.allocate(48);

        //1.放入缓存的方法，从channel读取
        int read = fileChannel.read(buf);

        //2.放入缓存的方法，自己手动放进去
        String str = "zhuopeng";
        byte[] b = str.getBytes();
        buf.put(b);

        while (read != -1) {
            //切换为读模式
            buf.flip();
            //标记当前的position
            buf.mark();
            while (buf.hasRemaining()){
                System.out.print((char)buf.get());//一次读取一个byte
            }
            //重新回到当前的position
            buf.reset();
            //将buf中的内容写到另一个channel中
            int write = fileChannel2.write(buf);

            buf.clear();
            read = fileChannel.read(buf);
        }
        aFile.close();

    }
}

 

 

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