randomfiletest.java

java培训专题

package io;
import java.io.*;
public class RandomFileTest{

	
	public static void main(String[] args) throws Exception{
		Student st1=new Student(1,"zhangsan",98.5);
		Student st2=new Student(2,"lishi",96.5);
		Student st3=new Student(3,"wangwu",78.5);
		RandomAccessFile raf=new RandomAccessFile("student.txt","rw");
		st1.writeStudent(raf);
		st2.writeStudent(raf);
		st3.writeStudent(raf);//当读取第三个学生信息的时候,文件指针已经指向了文件的末尾.
		Student s=new Student();
		raf.seek(0);//将文件指针重新定向为指向文件的开头.否则报出EOF异常.
		for(long i=0;i<raf.length();i=raf.getFilePointer()){/*raf.length()返回文件长度,返回的值是long型;
		和raf.getFilePointer()返回些文件的当前
	    返回的都是long类型
		*/
			s.readStudent(raf);
			System.out.println(s.num+":"+s.name+":"+s.score);
		}
		raf.close();
	}

}
class Student {
	int num;
    String name;
    double score;
    public Student(){	
    }
    public Student(int num,String name,double score){
    	this.num=num;
    	this.name=name;
    	this.score=score;
    }
    public void writeStudent(RandomAccessFile raf)throws Exception{
    	raf.writeInt(num);
    	raf.writeUTF(name);//读取String类型的数据,并把这个字符串的长度记录在其中.而writeChar()则无此功能
    	raf.writeDouble(score);
    }
    public void readStudent(RandomAccessFile raf)throws Exception{
    	num=raf.readInt();
    	name=raf.readUTF();
    	score=raf.readDouble();
    }
}

/*import java.io.*;

class RandomFileTest
{
	public static void main(String[] args) throws Exception
	{
		Student s1=new Student(1,"zhangsan",98.5);
		Student s2=new Student(2,"lisi",96.5);
		Student s3=new Student(3,"wangwu",78.5);
		RandomAccessFile raf=new RandomAccessFile("student.txt","rw");
		s1.writeStudent(raf);
		s2.writeStudent(raf);
		s3.writeStudent(raf);
		
		Student s=new Student();
		raf.seek(0);
		for(long i=0;i<raf.length();i=raf.getFilePointer())
		{
			s.readStudent(raf);
			System.out.println(s.num+":"+s.name+":"+s.score);
		}
		raf.close();
	}
}

class Student
{
	int num;
	String name;
	double score;
	public Student()
	{
	}
	public Student(int num,String name,double score)
	{
		this.num=num;
		this.name=name;
		this.score=score;
	}
	public void writeStudent(RandomAccessFile raf) throws IOException
	{
		raf.writeInt(num);
		raf.writeUTF(name);
		raf.writeDouble(score);
	}
	public void readStudent(RandomAccessFile raf) throws IOException
	{
		num=raf.readInt();
		name=raf.readUTF();
		score=raf.readDouble();
	}
}*/