head first java ( 14章 )

- 对象的状态和行为

对象有状态和行为两种属性, 行为存在于类中, 状态存在于个别对象中( 想内存 )

- 保存状态的两种方法

比如你编写了一个游戏程序, 里边有精灵, 矮人, 魔法师, 你肯定需要保存他们的状态, 比如生命值, 武力值等等, 那么如何保存呢?

- 创建序列化对象写入文件步骤

- 在堆上的对象 –> 被实例化的对象

如果存储的实例变量不仅仅是标量类型, 如果是引用类型怎么办? 存储的目的在于恢复, 如果恢复实例变量是引用类型呢 ?

当对象被序列化时, 被该对象引用的实例变量也会被序列化，且所有被引用的对象也会被序列化，最棒的是，这些操作都是自动的

- 如果要让类能被序列化, 就必须实现 Serializable 接口

例如 public class Box implements Serializable { // 这个接口没有方法需要实现, 只是说明这个类可以被序列化

objectOutputStream.writeobject(myBox); // 这个myBox 类必须实现 Serializable 接口

如果某实例变量不能或不应该被序列化, 就把它标记为 transient(瞬时)的

transient String currentID;

- 解序列化, 还原对象

- 存储与恢复游戏人物源码及分析

GameTest/*
 * File: GameSaveTest.java
 * ------------------------------
 * 
 */

import java.io.*;


public class GameSaveTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		GameCharacter one = new GameCharacter(50, "Elf", new String[] {"bow", "swod", "dust"});
		GameCharacter two = new GameCharacter(200, "Troll", new String[] {"bare hands", "big ax"});
		GameCharacter three = new GameCharacter(120, "Magician", new String[] {"spells", "invisibility"});
		
		try {
			ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream("Game.ser"));
			os.writeObject(one);
			os.writeObject(two);
			os.writeObject(three);
			os.close();
		} catch (IOException ex) {
			ex.printStackTrace();
		}
		one = null;
		two = null;
		three = null;
		
		try {
			ObjectInputStream is = new ObjectInputStream(new FileInputStream("Game.ser"));
			GameCharacter oneRestore = (GameCharacter) is.readObject();
			GameCharacter twoRestore = (GameCharacter) is.readObject();
			GameCharacter threeRestore = (GameCharacter) is.readObject();
			
			System.out.println("One's type: " + oneRestore.getType());
			System.out.println("Two's type: " + twoRestore.getType());
			System.out.println("Three's type: " + threeRestore.getType());
		} catch (Exception ex) {
			ex.printStackTrace();
		}
		
		
	}

}

GameCharacter/*
 * File: GameCharacter.java
 * ----------------------------
 * 
 */

import java.io.*;

public class GameCharacter implements Serializable {
	
	
	/* 
	 * structure function 
	 * augument p: power
	 * arugment t: type
	 * argument w: weapons
	 */
	public GameCharacter(int p, String t, String[] w) {
		power = p;
		type = t;
		weapons = w;
	}
	
	public int getPower() {
		return power;
	}
	
	public String getType() {
		return type;		
	}
	
	public String getWeapons() {
		String weaponList = "";
		
		for (int i=0; i<weapons.length; i++) {
			weaponList += weapons[i] + "";
			
		}
		return weaponList;
	}
		
/* private instance values */
	private int power;
	String type;
	String[] weapons;

	
}