IO流对应代码

package com.seecen.javaApi;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.RandomAccessFile;

import org.junit.Test;

public class TestRandomAccessFile {


   public void testWrite() throws Exception{
//       1.创建能够读写的RandomAccessFile类的对象
       RandomAccessFile raf = new RandomAccessFile("raf.txt","rw");
//       2.使用write方法向文件raf.txt写入数组1
//       该方法写出的是一个字节,写出的是int值的低8位
       raf.write(111);
       raf.close();
   }


   public void testRead()throws Exception {
//       1.创建能够读写的RandomAccessFile类的对象
       RandomAccessFile raf = new RandomAccessFile("raf.txt","r");
//       2.读取一个字节
       int a = raf.read();
       System.out.println(a);
       raf.close();
   }


   public void testGetFilePointer() throws Exception{
//       1.创建能够读写的RandomAccessFile类的对象
       RandomAccessFile raf = new RandomAccessFile("raf.txt","rw");
       raf.write('A');//字母占一个字节
       System.out.println(raf.getFilePointer());
       raf.writeInt(3);//int类型的数据占4个字节
       System.out.println(raf.getFilePointer());

//       测试Seek方法
//       将指针移动到文件的开始处(第一个字节的位置)
       raf.seek(0);
       System.out.println(raf.getFilePointer());
       raf.close();
   }



//   测试批量写出
   public void testWriteByteArray() throws Exception{
//       1.创建能够读写的RandomAccessFile类的对象
       RandomAccessFile raf = new RandomAccessFile("raf.txt","rw");
//       2.使用write(byte[])方法将字符串"HelloWorld"写入
       byte[] buf = "HelloWorld".getBytes();
       raf.write(buf);
//       查看大小
       System.out.println(raf.length());
       raf.close();
   }



//   测试批量读取
   public void testReadByteArray() throws Exception{
//       1.创建能够读写的RandomAccessFile类的对象
       RandomAccessFile raf = new RandomAccessFile("raf.txt","r");
//       创建一个字节数组,长度为10
       byte[] buf = new byte[10];
       int len = raf.read(buf);
       System.out.println("读取到了:"+len+"个字节");
       System.out.println(new String(buf));
//       获取文件raf.txt指针
       System.out.println("指针的位置:"+raf.getFilePointer());//10
//       设置指针读取world
       raf.seek(0);
       raf.skipBytes(5);
       System.out.println("指针的位置:"+raf.getFilePointer());//5
//
       byte[] buf1 = new byte[5];
       int len1 = raf.read(buf1);
       System.out.println(new String(buf1));
       raf.close();
       }


   public void testFileOutputStream() throws Exception{
       FileOutputStream fos = new FileOutputStream("raf.txt");
       byte[] buf = "HelloWorld".getBytes();
       fos.write(buf);
       FileOutputStream fos1 = new FileOutputStream("raf.txt",true);
       byte[] buf1 = "你好".getBytes();
       fos1.write(buf1);
       fos.close();
       fos1.close();
       }


   @Test
   public void testFileInputStream() throws Exception{
       FileInputStream fis = new FileInputStream("raf.txt");
       byte[] a = new byte[2];
       fis.read(a);
       System.out.println(new String(a));
   }

}

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