Java—IO流 RandomAccessFile类

package com.test.io;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Arrays;

public class RafDemo {

    public static void main(String[] args) throws IOException {
        File demo = new File("demo");
        if (!demo.exists()) {
            demo.mkdir();
        }
        File file = new File(demo, "raf.dat");
        if (!file.exists()) {
            file.createNewFile();
        }
        RandomAccessFile raf = new RandomAccessFile(file, "rw");
        System.out.println(raf.getFilePointer());
        
        raf.write(‘A‘);//一个char型占两个字节，但是write一次只写入一个字节（A字符的后八位）
        System.out.println(raf.getFilePointer());
        raf.write(‘B‘);
        
        int i = 0x7fffffff;
        raf.write(i >>> 24);//写入i的高八位
        raf.write(i >>> 16);
        raf.write(i >> 8);
        raf.write(i);
        System.out.println(raf.getFilePointer());
        //直接写入一个int
        raf.writeInt(i);
        
        String s = "你";
        byte[] b = s.getBytes("utf8");
        raf.write(b);
        System.out.println(raf.length());
        
        //读文件，必须把指针移到头部
        raf.seek(0);
        //一次性读取，把文件中的内容都读到字节数组中
        byte[] buf = new byte[(int) raf.length()];
        raf.read(buf);
        System.out.println(Arrays.toString(buf));
        for (byte c : buf) {
            System.out.print(Integer.toHexString(c & 0xff) + "  ");
        }
        //关闭文件
        raf.close();
    }

}

0
1
6
13
[65, 66, 127, -1, -1, -1, 127, -1, -1, -1, -28, -67, -96]
41  42  7f  ff  ff  ff  7f  ff  ff  ff  e4  bd  a0