studentfile.java

《Java2程序设计实用教程(第2版)》课件

//【例9.4】  将若干学生对象写入一个对象文件中。


import java.io.*;

public class StudentFile 
{
    private String filename;
    
    public StudentFile(String filename)
    {
        this.filename = filename;
    }
    
    public void writeToFile() throws IOException           //向指定文件写入若干学生对象
    {
        FileOutputStream fout = new FileOutputStream(this.filename);
        ObjectOutputStream objout = new ObjectOutputStream(fout);
        objout.writeObject(new Student("杨柳"));           //写入一个对象
        objout.writeObject(new Student("明明"));
        objout.writeObject(new Student("小玲"));
        objout.close();                                     //先关闭对象流
        fout.close();                                       //再关闭文件流
        System.out.println("Write Student to File "+this.filename);
    }

    public void readFromFile() throws IOException          //从指定文件中读取若干学生对象
    {
        FileInputStream fin = new FileInputStream(this.filename);
        ObjectInputStream objin = new ObjectInputStream(fin);
        System.out.println("readFromFile "+this.filename);

        while (true)                                       //输入流未结束时
            try
            {
                Student stu = (Student)objin.readObject(); //读取一个对象
                System.out.println(stu.toString()+"  ");
            }
            catch (Exception e)
            {
                break;
            }
        objin.close();                                     //先关闭对象流
        fin.close();                                       //再关闭文件流
    }

    public Student[] openFile() throws IOException         //返回从指定文件中读取的学生对象数组
    {
        FileInputStream fin = new FileInputStream(this.filename);
        ObjectInputStream objin = new ObjectInputStream(fin);

        Student[] students = new Student[20];
        int i=0;
        while (true)
            try
            {
                students[i] = (Student)objin.readObject(); //读取一个对象
                i++;
            }
            catch (Exception e)    //捕获IOException和ClassNotFoundException异常
            {
                break;
            }
        objin.close();                                     //先关闭对象流
        fin.close();                                       //再关闭文件流
        return students;
    }

    public static void main(String args[]) throws IOException
    {
        StudentFile afile = new StudentFile("StudentFile.dat");
        afile.writeToFile();
        afile.readFromFile();
    }
}


/*
程序运行结果如下：
Write Fibonacci to File StudentFile.dat 
readFromFile StudentFile.dat
1  杨柳
2  明明
3  小玲
*/