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serialVersionUID， ObjectInputStream与ObjectOutputStream类，Serializable接口，serialVersionUID的作用和用法

ObjectInputStream与ObjectOutputStream类所读写的对象必须实现Serializable接口，对象中的transient和static类型成员变量不会被读取和写入

Serializable其实是一个空接口

package java.io;
 
public interface Serializable {
}

Serializable是一个空接口，没有什么具体内容，它的目的只是简单的标识一个类的对象可以被序列化。什么情况下需要序列化

a）当你想把的内存中的对象写入到硬盘的时候；

b）当你想用套接字在网络上传送对象的时候；

c）当你想通过RMI传输对象的时候；再稍微解释一下:a)比如说你的内存不够用了，那计算机就要将内存里面的一部分对象暂时的保存到硬盘中，等到要用的时候再读入到内存中，硬盘的那部分存储空间就是所谓的虚拟内存。在比如过你要将某个特定的对象保存到文件中，我隔几天在把它拿出来用，那么这时候就要实现Serializable接口；

public static void main(String args[]) throws Exception {
 
        class Student implements Serializable {
 
            private static final long serialVersionUID = 0xbc9903f7986df52fL;
 
            String name;
            int id ;
            int age;
            String department;
            public Student(String name, int id, int age, String department) {
                this.age = age;
                this.department = department;
                this.id = id;
                this.name = name;
            }
        }
 
        Student s1=new Student("张2三", 1, 5, "化学");
        Student s2=new Student("李四1", 2, 9, "生物");
 
        FileOutputStream fout = new FileOutputStream("C:\\student.txt");
        ObjectOutputStream out=new ObjectOutputStream(fout);
        out.writeObject(s1);
        out.writeObject(s2);
        out.close();
        FileInputStream fin=new FileInputStream("C:\\student.txt");
        ObjectInputStream in=new ObjectInputStream(fin);
        try {
            s1=(Student) in.readObject();
            s2=(Student) in.readObject();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        in.close();
        System.out.print("name:"+s1.name);
        System.out.print(" id:"+s1.id);
        System.out.print(" age:"+s1.age);
        System.out.println(" department:"+s1.department);
        System.out.print("name:"+s2.name);
        System.out.print(" id:"+s2.id);
        System.out.print(" age:"+s2.age);
        System.out.println(" department:"+s2.department);
    }