RandomAccessFile

1. RandomAccessFile类同时实现了DataInput和DataOutput接口，提供了对文件随机存取的功能，利用这个类可以在文件的任何位置读取或写人数据；
2. RandomAccessFile类提供了一个文件指针，用来标志要进行读写操作的下一数据的位置；
3. 该方法把文件的读入，写出，写到一起了，是操作文件比较好的方法；

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import java.io.*;class RandomAccessFileTest{    public static void main(String[] arg) throws Exception{        Student s1 = new Student(1,"zhangsan",95.5);        Student s2 = new Student(2,"lisi",96.5);        Student s3 = new Student(3,"wangwu",94);        RandomAccessFile raf = new RandomAccessFile("student.txt","rw");        s1.writeStudent(raf);        s2.writeStudent(raf);        s3.writeStudent(raf);        Student s = new Student();        raf.seek(0);//把指针的偏移量设置到0的位置；        for(long i=0 ; i < raf.length();i=raf.getFilePointer()){            s.readStudent(raf);            System.out.println("num="+s.num+"name="+s.name+"score="+s.score);        }        raf.close();    }}class Student{    int num;    String name;    double score;    Student(){}    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);        raf.writeDouble(score);         }    public void readStudent(RandomAccessFile raf) throws Exception{        num = raf.readInt();        name = raf.readUTF();        score = raf.readDouble();    }}