设计模式：状态模式
什么是状态模式
状态模式，又称状态对象模式（Pattern of Objects for States），状态模式是对象的行为模式。状态模式允许一个对象在其内部状态改变的时候改变其行为。这个对象看上去就像是改变了它的类一样。
状态模式的结构
-
Context（环境类）
-
State（抽象状态类）
-
ConcreteState（具体状态类）
状态模式的一个实例
有一个游戏，玩家等级分为四个等级，分别是Light、Medium、Hard和Devilish。等级越高权限越多。
实例代码
Level
public abstract class Level {
public abstract void play();
public abstract void doubleScore();
public abstract void changeCards();
public abstract void peekCards();
}
Light
public class Light extends Level {
@Override
public void play() {
System.out.println("Light play()");
}
@Override
public void doubleScore() {
System.out.println("Light doubleScore(). Not Support...");
}
@Override
public void changeCards() {
System.out.println("Light changeCards(). Not Support...");
}
@Override
public void peekCards() {
System.out.println("Light peekCards(). Not Support...");
}
}
Medium
public class Medium extends Level {
@Override
public void play() {
System.out.println("Medium play()");
}
@Override
public void doubleScore() {
System.out.println("Medium doubleScore().");
}
@Override
public void changeCards() {
System.out.println("Medium changeCards(). Not Support...");
}
@Override
public void peekCards() {
System.out.println("Medium peekCards(). Not Support...");
}
}
Hard
public class Hard extends Level {
@Override
public void play() {
System.out.println("Hard play()");
}
@Override
public void doubleScore() {
System.out.println("Hard doubleScore().");
}
@Override
public void changeCards() {
System.out.println("Hard changeCards().");
}
@Override
public void peekCards() {
System.out.println("Hard peekCards(). Not Support...");
}
}
Devilish
public class Devilish extends Level {
@Override
public void play() {
System.out.println("Devilish play()");
}
@Override
public void doubleScore() {
System.out.println("Devilish doubleScore().");
}
@Override
public void changeCards() {
System.out.println("Devilish changeCards().");
}
@Override
public void peekCards() {
System.out.println("Devilish peekCards().");
}
}
Player
public class Player {
private Level level;
private int score;
private String name;
public Player(String name){
level = new Light();
score = 0;
this.name = name;
System.out.println("Create Player:" + name);
}
public void setLevel(Level level) {
this.level = level;
}
public void addScore(int score){
this.score += score;
if (this.score < 100){
setLevel(new Light());
System.out.println("Current Level:Light. Now Score:" + this.score);
}else if (this.score < 200){
setLevel(new Medium());
System.out.println("Current Level:Medium. Now Score:" + this.score);
}else if (this.score < 300){
setLevel(new Hard());
System.out.println("Current Level:Hard. Now Score:" + this.score);
}else {
setLevel(new Devilish());
System.out.println("Current Level:Devilish. Now Score:" + this.score);
}
}
public void play(){
level.play();
}
public void doubleScore() {
level.doubleScore();
}
public void changeCards() {
level.changeCards();
}
public void peekCards() {
level.peekCards();
}
}
Client
public class Client {
public static void main(String[] args){
Player player = new Player("Jack");
player.addScore(50);
player.play();
player.doubleScore();
player.addScore(1000);
player.peekCards();
player.addScore(-800);
player.changeCards();
}
}
实例结果
Create Player:Jack
Current Level:Light. Now Score:50
Light play()
Light doubleScore(). Not Support...
Current Level:Devilish. Now Score:1050
Devilish peekCards().
Current Level:Hard. Now Score:250
Hard changeCards().
（完）