IO流之对象专属流

IO流之对象专属流

单个对象

以下代码把一个Java对象从内存中写入到硬盘，再读回到内存：

package com.javalearn.io.ObjectIO;

import java.io.*;

public class TestForObjIO {
    public static void main(String[] args) throws Exception{
        Student s = new Student(1111,"cxf");
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("file1"));
        oos.writeObject(s);  // 序列化
        oos.flush();
        oos.close();

        ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("file1"));
        Object obj = objectInputStream.readObject();  // 反序列化
        System.out.println(obj);  // 自动执行toString方法
        objectInputStream.close();
    }
}

class Student implements Serializable {  // 实现Serializable接口，才能序列化
    private int no;  // 若加上transient关键字，则此属性不参与序列化，反序列化时显示null
    private String name;
    public Student() {

    }
    public Student(int no,String name) {
        this.no = no;
        this.name = name;
    }

    public int getNo() {
        return no;
    }

    public void setNo(int no) {
        this.no = no;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Student{" +
                "no=" + no +
                ", name='" + name + '\'' +
                '}';
    }
}

输出结果：

Student{no=1111, name='cxf'}

多个对象

以下代码进行多个对象的IO：

package com.javalearn.io.objIOset;

import java.io.*;
import java.util.ArrayList;
import java.util.List;

public class TestForMultiObj {
    public static void main(String[] args) throws Exception{
        List<User> userList = new ArrayList<>();  // 用集合装载对象
        userList.add(new User(1,"cxf"));
        userList.add(new User(2,"smf"));
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("file1"));
        oos.writeObject(userList);  // 把集合序列化
        oos.flush();
        oos.close();
        ObjectInputStream ois  =new ObjectInputStream(new FileInputStream("file1"));
        List<User> userList1 = (List<User>) ois.readObject();  // 反序列化
        for(User user:userList1) {
            System.out.println(user);
        }
        ois.close();
    }
}

class User implements Serializable {
    private int no;
    private String name;

    public User() {
    }

    public User(int no, String name) {
        this.no = no;
        this.name = name;
    }

    @Override
    public String toString() {
        return "User{" +
                "no=" + no +
                ", name='" + name + '\'' +
                '}';
    }
}

输出结果：

User{no=1, name='cxf'}
User{no=2, name='smf'}