黑马程序员：java IO randomAccessFile类

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我是靠谱客的博主曾经野狼，最近开发中收集的这篇文章主要介绍黑马程序员：java IO randomAccessFile类，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

randomAccessFile 类（随机访问）对等长格式的记录访问有很大优势如：学生成绩，员工信息。

两种构造方法： new randomAccessFile(file,"rw") // 可读写

new ramdomAccessFile(file,"r") // 只读

例子：
/**
* @author cui
* 定义员工信息
*/
public class Employee {

/**
* @param args
*
*/
public String name=null;
public int    age=0;
public static final int LEN=8;
public Employee(String name,int age)
{
  if(name.length()>LEN)
  {
    name=name.substring(0,LEN);
  }
  else
  {
   while (name.length() <LEN)
   {
      name += "/u0000";
   }
  }
  this.name=name;
  this.age=age;
}

}
import java.io.IOException;
import java.io.RandomAccessFile;
/**
*
*/

/**
* @author cui
* 存储读取员工信息
*
*/
public class randomFileTest {

/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
  // TODO Auto-generated method stub
    Employee e1= new Employee("张三",21);
    Employee e2= new Employee("李四",24);
    Employee e3= new Employee("wangwu",27);

    RandomAccessFile ra=new RandomAccessFile("employee.txt","rw");
      ra.writeChars(e1.name); //writeChars 读取所有字符用的unicode编码占2字节所以后面读取跳过字节乘2
                                                 // ra.write(e1.name.getBytes());
      ra.writeInt(e1.age);   //输入整数个字节
      ra.writeChars(e2.name);
                    //ra.write(e2.name.getBytes());
      ra.writeInt(e2.age);
      ra.writeChars(e3.name);
                     // ra.write(e3.name.getBytes());
      ra.writeInt(e3.age);

       ra.close(); //关闭


   //   int len=0;
      // byte[] buf= new byte[Employee.LEN];
      String strName="";
     RandomAccessFile raf =new RandomAccessFile("employee.txt","r");
     raf.skipBytes(Employee.LEN*2+4); //skipBytes(N)跳转N位
     for(int i=0;i<Employee.LEN;i++)
     {
      strName += raf.readChar(); //读取单个字节所以循环
     }
   // len =raf.read(buf);
   // strName = new String(buf,0,len);
     System.out.println(strName.trim()+":"+raf.readInt());//读取整数个字节
      strName="";
     raf.seek(0); // 定位到某处
     for(int i=0;i<Employee.LEN;i++)
     {
      strName += raf.readChar();
     }
    // len =raf.read(buf);
    // strName =new String(buf,0,len);
     System.out.println(strName.trim()+":"+raf.readInt());
      strName="";
     raf.skipBytes(Employee.LEN*2+4);
     for(int i=0;i<Employee.LEN;i++)
     {
      strName += raf.readChar();
     }
   // len =raf.read(buf);
   // strName =new String(buf,0,len);
     System.out.println(strName.trim()+":"+raf.readInt());
     raf.close();
   //方法 trim() 去掉不可见字符
}