transient 做个标记

import java.io.*;
import java.util.*;

public class Logon implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private Date date = new Date();
    private String username;
    private transient String password;

    Logon(String name, String pwd) {
        username = name;
        password = pwd;
    }

    public String toString() {
        String pwd = (password == null) ? "(n/a)" : password;
        return "logon info: 
 " + "username: " + username + "
 date: "
                + date.toString() + "
 password: " + pwd;
    }

    public static void main(String[] args) {
        Logon a = new Logon("Hulk", "myLittlePony");
        System.out.println("logon a = " + a);
        try {
            ObjectOutputStream o = new ObjectOutputStream(new FileOutputStream(
                    "Logon.out"));
            o.writeObject(a);
            o.close();
            // Delay:
            int seconds = 5;
            long t = System.currentTimeMillis() + seconds * 1000;
            while (System.currentTimeMillis() < t)
                ;
            // Now get them back:
            ObjectInputStream in = new ObjectInputStream(new FileInputStream(
                    "Logon.out"));
            System.out.println("Recovering object at " + new Date());
            a = (Logon) in.readObject();
            System.out.println("logon a = " + a);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}