随机存取对象RandomAccessFile

package other;

import java.io.IOException;
import java.io.RandomAccessFile;

public class RandomAccessFileDemo {

    public static void main(String[] args) throws IOException {
        // writeFile();
        // readFile();
         writeFile_2();
    }

    public static void writeFile() throws IOException {

        RandomAccessFile raf = new RandomAccessFile("ran.txt", "rw");

        raf.write("李四".getBytes());
        raf.writeInt(97); 
        raf.write("王五".getBytes());
        raf.writeInt(99);
        raf.close();
    }

    // 演示随机写
    public static void writeFile_2() throws IOException {

        RandomAccessFile raf = new RandomAccessFile("ran.txt", "rw");

        raf.seek(8*3);      //可以实现数据的分段写入，多个线程分别在不同的位置写入数据，不会互相影响
        raf.write("李二".getBytes());
        raf.writeInt(103); // 只写int类型的最低 8 位
        raf.close();
    }

    // 演示随机读
    public static void readFile() throws IOException {

        RandomAccessFile raf = new RandomAccessFile("ran.txt", "r");

        // 指定指针的位置
        raf.seek(8);

        // 跳过指定的字节数
        // raf.skipBytes(8);

        byte[] buf = new byte[4];
        raf.read(buf);

        String name = new String(buf);
        System.out.println(name);

        int age = raf.readInt();
        System.out.println(age);

        raf.close();
    }
}