Java中IO流 RandomAccessFile类实例详解

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