JAVA的设计模式浅谈

来源：互联网发布：一键切换ip mac 编辑：程序博客网时间：2024/05/05 11:49

java设计模式，本人贴上自己写的各种模式的实现代码来讲解；希望大家能学到。

BY-- 何泽江(凯捷国际)

创建模式

1.工厂方法模式（Factory Method）将程序中创建对象的操作，单独出来处理，创建一个产品的工厂接口，把实际的工作转移到具体的子类。大大提高了系统扩展的柔性，接口的抽象化处理给相互依赖的对象创建提供了最好的抽象模式。

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public class TestFactoryMethod {
public static void main(String[] args) {
AnimalFactory af=new DogFactory();
Animal1 a=af.getAnimal();
}
}
abstract class Animal1{}
class Dog1 extends Animal1{}
class Cat1 extends Animal1{}
abstract class AnimalFactory{
public abstract Animal1 getAnimal();
}
class DogFactory extends AnimalFactory{
public Animal1 getAnimal(){
System.out.println("Dog");
return new Dog1();
}
}
class CatFactory extends AnimalFactory{
public Animal1 getAnimal(){
System.out.println("Cat");
return new Cat1();
}
}

public class TestFactoryMethod { public static void main(String[] args) { AnimalFactory af=new DogFactory(); Animal1 a=af.getAnimal(); } } abstract class Animal1{} class Dog1 extends Animal1{} class Cat1 extends Animal1{} abstract class AnimalFactory{ public abstract Animal1 getAnimal(); } class DogFactory extends AnimalFactory{ public Animal1 getAnimal(){ System.out.println("Dog"); return new Dog1(); } } class CatFactory extends AnimalFactory{ public Animal1 getAnimal(){ System.out.println("Cat"); return new Cat1(); } }

2.抽象工厂模式（Abstract Factory）针对多个产品等级的情况，而工厂方法模式针对单一产品等级的情况。

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import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class TestAbstractFactory {
public static void main(String[] args) {
GUIFactory fact=new SwingFactory();
Frame f=fact.getFrame();
Component c1=fact.getButton();
Component c2=fact.getTextField();
f.setSize(500,300);
f.setLayout(new FlowLayout());
f.add(c1);
f.add(c2);
f.setVisible(true);
f.addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
System.exit(0);
}
});
}
}
abstract class GUIFactory{
public abstract Component getButton();
public abstract Component getTextField();
public abstract Frame getFrame();
}
class AWTFactory extends GUIFactory{
public Component getButton() {
return new Button("AWT Button");
}
public Frame getFrame() {
return new Frame("AWT Frame");
}
public Component getTextField() {
return new TextField(20);
}
}
class SwingFactory extends GUIFactory{
public Component getButton() {
return new JButton("Swing Button");
}
public Frame getFrame() {
return new JFrame("Swing Frame");
}
public Component getTextField() {
return new JTextField(20);
}
}

import java.awt.*; import javax.swing.*; import java.awt.event.*; public class TestAbstractFactory { public static void main(String[] args) { GUIFactory fact=new SwingFactory(); Frame f=fact.getFrame(); Component c1=fact.getButton(); Component c2=fact.getTextField(); f.setSize(500,300); f.setLayout(new FlowLayout()); f.add(c1); f.add(c2); f.setVisible(true); f.addWindowListener(new WindowAdapter(){ public void windowClosing(WindowEvent e){ System.exit(0); } }); } } abstract class GUIFactory{ public abstract Component getButton(); public abstract Component getTextField(); public abstract Frame getFrame(); } class AWTFactory extends GUIFactory{ public Component getButton() { return new Button("AWT Button"); } public Frame getFrame() { return new Frame("AWT Frame"); } public Component getTextField() { return new TextField(20); } } class SwingFactory extends GUIFactory{ public Component getButton() { return new JButton("Swing Button"); } public Frame getFrame() { return new JFrame("Swing Frame"); } public Component getTextField() { return new JTextField(20); } }

3.单例模式（Singleton）改善全局变量和命名空间的冲突，可以说是一种改良了的全局变量。这种一个类只有一个实例，且提供一个访问全局点的方式，更加灵活的保证了实例的创建和访问约束。系统中只有一个实例，因此构造方法应该为私有饿汉式：类加载时直接创建静态实例懒汉式：第一次需要时才创建一个实例，那么newInstance方法要加同步饿汉式比懒汉式要好，尽管资源利用率要差。但是不用同步。

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public class TestSingleton {
public static void main(String[] args) {
}
}
class ClassA{ //饿汉式
private static ClassA i=new ClassA();
public static ClassA newInstance(){
return i;
}
private ClassA(){}
}
class ClassB{ //懒汉式
private static ClassB i=null;
public static synchronized ClassB newInstance(){
if (i==null) i=new ClassB();
return i;
}
private ClassB(){}
}

public class TestSingleton { public static void main(String[] args) { } } class ClassA{ //饿汉式 private static ClassA i=new ClassA(); public static ClassA newInstance(){ return i; } private ClassA(){} } class ClassB{ //懒汉式 private static ClassB i=null; public static synchronized ClassB newInstance(){ if (i==null) i=new ClassB(); return i; } private ClassB(){} }

4.建造模式（Builder）将一个对象的内部表象和建造过程分割，一个建造过程可以造出不同表象的对象。可简化为模版方法模式.

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public class TestBuilder {
public static void main(String[] args) {
Builder b=new BuilderImpl1();
Director d=new Director(b);
Product p=d.createProduct();
}
}
interface Builder{
void buildPart1();
void buildPart2();
void buildPart3();
Product getProduct();
}
class BuilderImpl1 implements Builder{
public void buildPart1() {
System.out.println("create part1");
}
public void buildPart2() {
System.out.println("create part2");
}
public void buildPart3() {
System.out.println("create part3");
}
public Product getProduct() {
return new Product();
}
}
class Director{
Builder b;
public Director(Builder b){
this.b=b;
}
public Product createProduct(){
b.buildPart1(); b.buildPart2();
b.buildPart3();
return b.getProduct();
}
}
class Product{}

public class TestBuilder { public static void main(String[] args) { Builder b=new BuilderImpl1(); Director d=new Director(b); Product p=d.createProduct(); } } interface Builder{ void buildPart1(); void buildPart2(); void buildPart3(); Product getProduct(); } class BuilderImpl1 implements Builder{ public void buildPart1() { System.out.println("create part1"); } public void buildPart2() { System.out.println("create part2"); } public void buildPart3() { System.out.println("create part3"); } public Product getProduct() { return new Product(); } } class Director{ Builder b; public Director(Builder b){ this.b=b; } public Product createProduct(){ b.buildPart1(); b.buildPart2(); b.buildPart3(); return b.getProduct(); } } class Product{}

5.原型模式（ProtoType）通过一个原型对象来创建一个新对象（克隆）。Java中要给出Clonable接口的实现，具体类要实现这个接口，并给出clone()方法的实现细节，这就是简单原型模式的应用。 浅拷贝：只拷贝简单属性的值和对象属性的地址 深拷贝：拷贝本对象引用的对象，有可能会出现循环引用的情况。可以用串行化解决深拷贝。写到流里再读出来，这时会是一个对象的深拷贝结果。

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import java.io.*;
public class TestClonealbe {
public static void main(String[] args) throws Exception {
Father f=new Father();
User u1=new User("123456",f);
User u2=(User)u1.clone();
System.out.println(u1==u2);
System.out.println(u1.f==u2.f);
}
}
class User implements Cloneable,Serializable{
String password;
Father f;
public User(String password,Father f){
this.password=password;
this.f=f;
}
public Object clone() throws CloneNotSupportedException {
//return super.clone();
ObjectOutputStream out=null;
ObjectInputStream in=null;
try {
ByteArrayOutputStream bo=new ByteArrayOutputStream();
out = new ObjectOutputStream(bo);
out.writeObject(this);
out.flush();
byte[] bs=bo.toByteArray();
ByteArrayInputStream bi=new ByteArrayInputStream(bs);
in = new ObjectInputStream(bi);
Object o=in.readObject();
return o;
} catch (IOException e) {
e.printStackTrace();
return null;
} catch (ClassNotFoundException e) {
e.printStackTrace();
return null;
}
finally{
try {
out.close();
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
class Father implements Serializable{}

import java.io.*; public class TestClonealbe { public static void main(String[] args) throws Exception { Father f=new Father(); User u1=new User("123456",f); User u2=(User)u1.clone(); System.out.println(u1==u2); System.out.println(u1.f==u2.f); } } class User implements Cloneable,Serializable{ String password; Father f; public User(String password,Father f){ this.password=password; this.f=f; } public Object clone() throws CloneNotSupportedException { //return super.clone(); ObjectOutputStream out=null; ObjectInputStream in=null; try { ByteArrayOutputStream bo=new ByteArrayOutputStream(); out = new ObjectOutputStream(bo); out.writeObject(this); out.flush(); byte[] bs=bo.toByteArray(); ByteArrayInputStream bi=new ByteArrayInputStream(bs); in = new ObjectInputStream(bi); Object o=in.readObject(); return o; } catch (IOException e) { e.printStackTrace(); return null; } catch (ClassNotFoundException e) { e.printStackTrace(); return null; } finally{ try { out.close(); in.close(); } catch (IOException e) { e.printStackTrace(); } } } } class Father implements Serializable{}

结构模式如何把简单的类根据某种结构组装为大的系统

6.适配器模式（Adapter）在原类型不做任何改变的情况下，用一个适配器类把一个接口转成另一个接口，扩展了新的接口，灵活且多样的适配一切旧俗。这种打破旧框框，适配新格局的思想，是面向对象的精髓。以继承方式实现的类的 Adapter模式和以聚合方式实现的对象的Adapter模式，各有千秋，各取所长。

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public class TestAdapter {
public static void main(String[] args) {
USB mouse=new Mouse();
PC pc=new PC();
//pc.useMouse(mouse);
PS2 adapter=new USB2PS2Adapter(mouse);
pc.useMouse(adapter);
}
}
interface PS2{
void usePs2();
}
interface USB{
void useUsb();
}
class Mouse implements USB{
public void useUsb(){
System.out.println("通过USB接口工作");
}
}
class PC{
public void useMouse(PS2 ps2Mouse){
ps2Mouse.usePs2();
}
}
class USB2PS2Adapter implements PS2{
private USB usb;
public USB2PS2Adapter(USB usb) {
this.usb = usb;
}
public void usePs2(){
System.out.println("把对usePS2的方法调用转换成对useUSB的方法调用");
usb.useUsb();
}
}

public class TestAdapter { public static void main(String[] args) { USB mouse=new Mouse(); PC pc=new PC(); //pc.useMouse(mouse); PS2 adapter=new USB2PS2Adapter(mouse); pc.useMouse(adapter); } } interface PS2{ void usePs2(); } interface USB{ void useUsb(); } class Mouse implements USB{ public void useUsb(){ System.out.println("通过USB接口工作"); } } class PC{ public void useMouse(PS2 ps2Mouse){ ps2Mouse.usePs2(); } } class USB2PS2Adapter implements PS2{ private USB usb; public USB2PS2Adapter(USB usb) { this.usb = usb; } public void usePs2(){ System.out.println("把对usePS2的方法调用转换成对useUSB的方法调用"); usb.useUsb(); } }

7.组合模式（Composite）把整体和局部的关系用树状结构描述出来，使得客户端把整体对象和局部对象同等看待。

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import java.util.*;
public class TestComposite {
public static void main(String[] args) {
Node n1=new LeafNode(3);
Node n2=new LeafNode(4);
Node n3=new LeafNode(6);
Node n4=new LeafNode(5);
Node n5=new LeafNode(2);
Node n6=new LeafNode(9);
Node n7=new LeafNode(12);
Node n8=new LeafNode(7);
Node n9=new LeafNode(8);
Node c1=new CompositeNode(n1,n2,n3);
Node c4=new CompositeNode(n8,n9);
Node c3=new CompositeNode(n5,c4);
Node c2=new CompositeNode(n4,c3);
Node c5=new CompositeNode(n6,n7);
Node root=new CompositeNode(c1,c2,c5);
System.out.println(root.getValue());
}
}
abstract class Node{
public abstract int getValue();
}
class LeafNode extends Node{
int value;
public LeafNode(int value){
this.value=value;
}
public int getValue(){
return value;
}
}
class CompositeNode extends Node{
private List children=new ArrayList();
public CompositeNode(Node... nodes){
for(Node n:nodes){
children.add(n);
}
}
public int getValue(){
int result=0;
for(Node n:children){
result+=n.getValue();
}
return result;
}
}

import java.util.*; public class TestComposite { public static void main(String[] args) { Node n1=new LeafNode(3); Node n2=new LeafNode(4); Node n3=new LeafNode(6); Node n4=new LeafNode(5); Node n5=new LeafNode(2); Node n6=new LeafNode(9); Node n7=new LeafNode(12); Node n8=new LeafNode(7); Node n9=new LeafNode(8); Node c1=new CompositeNode(n1,n2,n3); Node c4=new CompositeNode(n8,n9); Node c3=new CompositeNode(n5,c4); Node c2=new CompositeNode(n4,c3); Node c5=new CompositeNode(n6,n7); Node root=new CompositeNode(c1,c2,c5); System.out.println(root.getValue()); } } abstract class Node{ public abstract int getValue(); } class LeafNode extends Node{ int value; public LeafNode(int value){ this.value=value; } public int getValue(){ return value; } } class CompositeNode extends Node{ private List children=new ArrayList(); public CompositeNode(Node... nodes){ for(Node n:nodes){ children.add(n); } } public int getValue(){ int result=0; for(Node n:children){ result+=n.getValue(); } return result; } }

8.装饰模式（Decorator）以对客户透明的方式来扩展对象的功能。用户根据功能需求随意选取组成对象的成分，通过方法的链式调用来实现。可以给对象动态的增加功能，比继承灵活性更大。

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public class TestDecorator {
public static void main(String[] args) {
Teacher t1=new SimpleTeacher();
Teacher t2=new CppTeacher(t1);
Teacher t3=new JavaTeacher(t2);
t3.teach();
//t.teach();
}
}
abstract class Teacher{
public abstract void teach();
}
class SimpleTeacher extends Teacher{
public void teach(){
System.out.println("Good Good Study, Day Day Up");
}
}
class JavaTeacher extends Teacher{
Teacher teacher;
public JavaTeacher(Teacher t){
this.teacher=t;
}
public void teach(){
teacher.teach();
System.out.println("Teach Java");
}
}
class CppTeacher extends Teacher{
Teacher teacher;
public CppTeacher(Teacher t){
this.teacher=t;
}
public void teach(){
teacher.teach();
System.out.println("Teach C++");
}
}

public class TestDecorator { public static void main(String[] args) { Teacher t1=new SimpleTeacher(); Teacher t2=new CppTeacher(t1); Teacher t3=new JavaTeacher(t2); t3.teach(); //t.teach(); } } abstract class Teacher{ public abstract void teach(); } class SimpleTeacher extends Teacher{ public void teach(){ System.out.println("Good Good Study, Day Day Up"); } } class JavaTeacher extends Teacher{ Teacher teacher; public JavaTeacher(Teacher t){ this.teacher=t; } public void teach(){ teacher.teach(); System.out.println("Teach Java"); } } class CppTeacher extends Teacher{ Teacher teacher; public CppTeacher(Teacher t){ this.teacher=t; } public void teach(){ teacher.teach(); System.out.println("Teach C++"); } }

9.代理模式（Proxy）用一个代理对象来作为另一个对象的代理，对客户来说是透明的。存在一个抽象主题类，具体主题类和代理主题类都继承（实现）抽象主题，代理主题类中的方法会调用具体主题类中相对应的方法。

10.享元模式（Flyweight Pattern）对象的状态分为内蕴状态和外蕴状态。内蕴状态不随环境变化而变化，因此可以作成系统共享.

11.门面模式（Facade）访问子系统的时候，通过一个Façade对象访问。Facade类是单例的。客户代码只需要和门面对象通信，不需要和具体子系统内部的对象通信，使得他们之间的耦合关系减弱。这次将表现层和逻辑层隔离，封装底层的复杂处理，为用户提供简单的接口，这样的例子随处可见。

门面模式很多时候更是一种系统架构的设计，在我所做的项目中，就实现了门面模式的接口，为复杂系统的解耦提供了最好的解决方案。

12.桥梁模式（Bridge）将抽象和实现脱耦，使得二者可以单独变化。使得一个继承关系不承担两个变化因素.使用合成来代替继承的一种体现.

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public YuanUser(BankAccount account) {
super(account);
}
public void getMoney() {
System.out.print("人民币");
account.withdraw();
}
public void saveMoney() {
System.out.print("人民币");
account.deposit();
}
}
class DollarUser extends BankUser{
public DollarUser(BankAccount account) {
super(account);
}
public void getMoney() {
System.out.print("美元");
account.withdraw();
}
public void saveMoney() {
System.out.print("美元");
account.deposit();
}
}

public YuanUser(BankAccount account) { super(account); } public void getMoney() { System.out.print("人民币"); account.withdraw(); } public void saveMoney() { System.out.print("人民币"); account.deposit(); } } class DollarUser extends BankUser{ public DollarUser(BankAccount account) { super(account); } public void getMoney() { System.out.print("美元"); account.withdraw(); } public void saveMoney() { System.out.print("美元"); account.deposit(); } }

行为模式描述如何在对象之间划分责任

13.策略模式（Strategy）如同LayoutManager和具体的布局管理器的关系，在抽象策略类中定义方法，将易于变化的部分封装为接口，通常Strategy 封装一些运算法则，使之能互换。Bruce Zhang在他的博客中提到策略模式其实是一种“面向接口”的编程方法，真是恰如其分。在具体策略子类中实现，客户代码根据不同的需要选择相应的具体类，例如电子商务中多种价格算法。一种策略一旦选中，整个系统运行期是不变化的

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public class TestStrategy {
public static void main(String[] args) {
Strategy s1=new May1Strategy();
Strategy s2=new June1Strategy();
Book b=new Book(100);
b.setS(s2);
System.out.println(b.getPrice());
}
}
class Book{
Strategy s;
public Book(double price){
this.price=price;
}
private double price;
public void setS(Strategy s) {
this.s = s;
}
public double getPrice(){
return price*s.getZheKou();
}
}
interface Strategy{
double getZheKou();
}
class May1Strategy implements Strategy{
public double getZheKou(){
return 0.8;
}
}
class June1Strategy implements Strategy{
public double getZheKou(){
return 0.7;
}
}

public class TestStrategy { public static void main(String[] args) { Strategy s1=new May1Strategy(); Strategy s2=new June1Strategy(); Book b=new Book(100); b.setS(s2); System.out.println(b.getPrice()); } } class Book{ Strategy s; public Book(double price){ this.price=price; } private double price; public void setS(Strategy s) { this.s = s; } public double getPrice(){ return price*s.getZheKou(); } } interface Strategy{ double getZheKou(); } class May1Strategy implements Strategy{ public double getZheKou(){ return 0.8; } } class June1Strategy implements Strategy{ public double getZheKou(){ return 0.7; } }

14.模板方法（Template Method）准备一个抽象类，把部分确定的逻辑定义在某些方法中，用其他抽象方法实现剩余的逻辑。不同子类对这些逻辑有不同的实现。用法：定义多个抽象操作，定义并实现一个模板方法，将步骤放在这个具体方法里，推迟到子类实现。子类可以改变父类的可变部分，但不能改变模板方法所代表的顶级逻辑。

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public class TestTemplateMethod {
public static void main(String[] args) {
XiaoPin xp=new DaPuKe();
xp.act();
}
}
abstract class XiaoPin{
public abstract void jiaoLiu();
public abstract void xuShi();
public abstract void gaoXiao();
public abstract void shanQing();
public final void act(){
jiaoLiu();
xuShi();
gaoXiao();
shanQing();
}
}
class DaPuKe extends XiaoPin{
public void jiaoLiu(){
System.out.println("顺口溜");
}
public void xuShi(){
System.out.println("火车除夕，老同学见面");
}
public void gaoXiao(){
System.out.println("名片当作扑克");
}
public void shanQing(){
System.out.println("马家军");
}
}

public class TestTemplateMethod { public static void main(String[] args) { XiaoPin xp=new DaPuKe(); xp.act(); } } abstract class XiaoPin{ public abstract void jiaoLiu(); public abstract void xuShi(); public abstract void gaoXiao(); public abstract void shanQing(); public final void act(){ jiaoLiu(); xuShi(); gaoXiao(); shanQing(); } } class DaPuKe extends XiaoPin{ public void jiaoLiu(){ System.out.println("顺口溜"); } public void xuShi(){ System.out.println("火车除夕，老同学见面"); } public void gaoXiao(){ System.out.println("名片当作扑克"); } public void shanQing(){ System.out.println("马家军"); } }

15.观察者模式（Observer）定义对象间的一种一对多的依赖关系,当一个对象的状态发生改变时, 所有依赖于它的对象都得到通知并被自动更新。观察者和被观察者的分开，为模块划分提供了清晰的界限。在低耦合的对象间完成协调。 Java中的事件模型就是一个应用。

16.迭代器模式（Iterator）类似于集合中的Iterator，使用迭代器来统一不同集合对象的遍历方式。在绝大多数的系统中，都会用到数组、集合、链表、队列这样的类型，关心迭代模式的来龙去脉非常有必要。在遍历算法中，迭代模式提供了遍历的顺序访问容器，GOF给出的定义为：提供一种方法访问一个容器（container）对象中各个元素，而又不需暴露该对象的内部细节。.NET中就是使用了迭代器来创建用于foreach的集合。

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public class TestIterator {
public static void main(String[] args) {
Stack s=new Stack();
s.push("Liucy");
s.push("Huxz");
s.push("George");
LinkedList l=new LinkedList();
l.addFirst("Liucy");
l.addFirst("Huxz");
l.addFirst("George");
print(l.iterator());
}
public static void print(Itr it){
while(it.hasNext()){
System.out.println(it.next());
}
}
}
interface Itr{
boolean hasNext();
Object next();
}
class Stack{
Object[] os=new Object[10];
int index=0;
private void expand(){
Object[] os2=new Object[os.length*2];
System.arraycopy(os,0,os2,0,os.length);
os=os2;
}
public void push(Object o){
if (index==os.length) expand();
os[index]=o;
index++;
}
public Object pop(){
index--;
Object o=os[index];
os[index]=null;
return o;
}
private class StackItr implements Itr{
int cursor=0;
public boolean hasNext(){

return cursor}
public Object next(){
return os[cursor++];
}
}
public Itr iterator(){
return new StackItr();
}
}
class LinkedList{
private class Node{
Object o;
Node next;
public Node(Object o){
this.o=o;
}
public void setNext(Node next){
this.next=next;
}
public Node getNext(){
return this.next;
}
}
Node head;
public void addFirst(Object o){
Node n=new Node(o);
n.setNext(head);
head=n;
}
public Object removeFirst(){
Node n=head;
head=head.getNext();
return n.o;
}
class LinkedListItr implements Itr{
Node currentNode=head;
public boolean hasNext(){
return this.currentNode!=null;
}
public Object next(){
Node n=currentNode;
currentNode=currentNode.getNext();
return n.o;
}
}
public Itr iterator(){
return new LinkedListItr();
}
}

public class TestIterator { public static void main(String[] args) { Stack s=new Stack(); s.push("Liucy"); s.push("Huxz"); s.push("George"); LinkedList l=new LinkedList(); l.addFirst("Liucy"); l.addFirst("Huxz"); l.addFirst("George"); print(l.iterator()); } public static void print(Itr it){ while(it.hasNext()){ System.out.println(it.next()); } } } interface Itr{ boolean hasNext(); Object next(); } class Stack{ Object[] os=new Object[10]; int index=0; private void expand(){ Object[] os2=new Object[os.length*2]; System.arraycopy(os,0,os2,0,os.length); os=os2; } public void push(Object o){ if (index==os.length) expand(); os[index]=o; index++; } public Object pop(){ index--; Object o=os[index]; os[index]=null; return o; } private class StackItr implements Itr{ int cursor=0; public boolean hasNext(){ return cursor} public Object next(){ return os[cursor++]; } } public Itr iterator(){ return new StackItr(); } } class LinkedList{ private class Node{ Object o; Node next; public Node(Object o){ this.o=o; } public void setNext(Node next){ this.next=next; } public Node getNext(){ return this.next; } } Node head; public void addFirst(Object o){ Node n=new Node(o); n.setNext(head); head=n; } public Object removeFirst(){ Node n=head; head=head.getNext(); return n.o; } class LinkedListItr implements Itr{ Node currentNode=head; public boolean hasNext(){ return this.currentNode!=null; } public Object next(){ Node n=currentNode; currentNode=currentNode.getNext(); return n.o; } } public Itr iterator(){ return new LinkedListItr(); } }

17.责任链（Chain of Responsibility）多个处理器对象连成一串，请求在这条链上传递，由该处理这个请求的处理器来处理。发出请求的客户端并不知道哪个对象处理请求。

[java] view plaincopyprint?

public class TestChain {
public static void main(String[] args) {
String pass1="123456";
String pass2="123456";
String personId="123456789012345678";
String email="chmask@163.com";
register(pass1,pass2,personId,email);
}
public static void register(String pass1,String pass2,String personId,String email){
Filter f1=new PasswordFilter1();
Filter f2=new PasswordFilter2();
Filter f3=new PersonIdFilter();
Filter f4=new EmailFilter();
f1.setNext(f2);
f2.setNext(f3);
f3.setNext(f4);
System.out.println(f1.doFilter(pass1,pass2,personId,email));
}
}
abstract class Filter{
Filter next=null;
public Filter getNext() {
return next;
}
public void setNext(Filter next) {
this.next = next;
}
public String doFilter(String pass1,String pass2,String personId,String email){
if (next==null) return "成功";
else return next.doFilter(pass1,pass2,personId,email);
}
}
class PasswordFilter1 extends Filter{
public String doFilter(String pass1,String pass2,String personId,String email){
if (!(pass1.equals(pass2)))
return "两次密码输入不一致";
else return super.doFilter(pass1,pass2,personId,email);
}
}
class PasswordFilter2 extends Filter{
public String doFilter(String pass1,String pass2,String personId,String email){
if (pass1.length()!=6)
return "密码长度必须为6";
else return super.doFilter(pass1,pass2,personId,email);
}
}
class PersonIdFilter extends Filter{
public String doFilter(String pass1,String pass2,String personId,String email){
if (personId.length()!=15 && personId.length()!=18)
return "身份证号码非法";
else return super.doFilter(pass1,pass2,personId,email);
}
}
class EmailFilter extends Filter{
public String doFilter(String pass1,String pass2,String personId,String email){
int i1=email.indexOf("@");
int i2=email.indexOf(".");
if (i1==-1 || i2==-1 || i2-i1<=1 || i1==0 || i2==email.length()-1)
return "email非法";
else return super.doFilter(pass1,pass2,personId,email);
}
}

public class TestChain { public static void main(String[] args) { String pass1="123456"; String pass2="123456"; String personId="123456789012345678"; String email="chmask@163.com"; register(pass1,pass2,personId,email); } public static void register(String pass1,String pass2,String personId,String email){ Filter f1=new PasswordFilter1(); Filter f2=new PasswordFilter2(); Filter f3=new PersonIdFilter(); Filter f4=new EmailFilter(); f1.setNext(f2); f2.setNext(f3); f3.setNext(f4); System.out.println(f1.doFilter(pass1,pass2,personId,email)); } } abstract class Filter{ Filter next=null; public Filter getNext() { return next; } public void setNext(Filter next) { this.next = next; } public String doFilter(String pass1,String pass2,String personId,String email){ if (next==null) return "成功"; else return next.doFilter(pass1,pass2,personId,email); } } class PasswordFilter1 extends Filter{ public String doFilter(String pass1,String pass2,String personId,String email){ if (!(pass1.equals(pass2))) return "两次密码输入不一致"; else return super.doFilter(pass1,pass2,personId,email); } } class PasswordFilter2 extends Filter{ public String doFilter(String pass1,String pass2,String personId,String email){ if (pass1.length()!=6) return "密码长度必须为6"; else return super.doFilter(pass1,pass2,personId,email); } } class PersonIdFilter extends Filter{ public String doFilter(String pass1,String pass2,String personId,String email){ if (personId.length()!=15 && personId.length()!=18) return "身份证号码非法"; else return super.doFilter(pass1,pass2,personId,email); } } class EmailFilter extends Filter{ public String doFilter(String pass1,String pass2,String personId,String email){ int i1=email.indexOf("@"); int i2=email.indexOf("."); if (i1==-1 || i2==-1 || i2-i1<=1 || i1==0 || i2==email.length()-1) return "email非法"; else return super.doFilter(pass1,pass2,personId,email); } }

18.状态模式（State）在对象内部状态改变时改变其行为。把所研究的对象的行为封装在不同的状态对象中。

[java] view plaincopyprint?

import static java.lang.System.*;
public class TestState {
public static void main(String[] args) {
BBSUser u=new BBSUser();
u.setState(new GuestState());
u.publish();
u.setState(new NormalState());
u.publish();
u.setState(new BlockedState());
u.publish();
u.setState(new NewComerState());
u.publish();
}
}
class BBSUser{
private State state;
public void setState(State state){
this.state=state;
}
public void publish(){
state.action();
}
}
abstract class State{
public abstract void action();
}
class GuestState extends State{
public void action(){
out.println("您处在游客状态，请先登录");
}
}
class NormalState extends State{
public void action(){
out.println("您处在正常状态，文章发表成功");
}
}
class BlockedState extends State{
public void action(){
out.println("您处在被封状态，文章发表失败");
}
}
class NewComerState extends State{
public void action(){
out.println("您是新手，请先学习一下，3天后再来");
}
}
class StateFactory{
public static State createState(int i){
if (i==1) return new GuestState();
else return new NormalState();
}
}

import static java.lang.System.*; public class TestState { public static void main(String[] args) { BBSUser u=new BBSUser(); u.setState(new GuestState()); u.publish(); u.setState(new NormalState()); u.publish(); u.setState(new BlockedState()); u.publish(); u.setState(new NewComerState()); u.publish(); } } class BBSUser{ private State state; public void setState(State state){ this.state=state; } public void publish(){ state.action(); } } abstract class State{ public abstract void action(); } class GuestState extends State{ public void action(){ out.println("您处在游客状态，请先登录"); } } class NormalState extends State{ public void action(){ out.println("您处在正常状态，文章发表成功"); } } class BlockedState extends State{ public void action(){ out.println("您处在被封状态，文章发表失败"); } } class NewComerState extends State{ public void action(){ out.println("您是新手，请先学习一下，3天后再来"); } } class StateFactory{ public static State createState(int i){ if (i==1) return new GuestState(); else return new NormalState(); } }

19.备忘录模式（Memento）备忘录对象用来存储另一个对象的快照对象，保存其内部状态，使得可以随时恢复。备忘录角色：保存发起人对象的内部状态，保护内容不被除发起人对象之外的对象获取。窄接口：负责人对象和其他对象看到的接口，只允许把备忘录对象传给其他对象。宽接口：发起人能看到的接口，允许读取内部状态。发起人角色：创建并使用备忘录对象来保存其状态负责人角色：负责保存备忘录对象。 白箱实现：备忘录类对其他类也可见，这样发起人的状态可能会存在安全问题。 黑箱实现：把备忘录类作成发起人的内部类，对外提供一个标识接口。

[java] view plaincopyprint?

public class TestMemento{
public static void main(String[] args){
Originator ori=new Originator();
Caretaker c=new Caretaker();
ori.setState("State 1");
IFMemento m=ori.createMemento();
c.save(m);
ori.setState("State 2");
m=c.retrieve();
ori.restore(m);
System.out.println("Now State:"+ori.getState());
}
}
class Originator{
String state;
public void setState(String s){
state=s;
System.out.println("State change to: "+s);
}
public String getState(){
return this.state;
}
public IFMemento createMemento(){
return new Memento(state);
}
public void restore(IFMemento m){
Memento mt=(Memento)m;
this.state=mt.getState();
}
private class Memento implements IFMemento{
private String state;
public Memento(String s){
this.state=s;
}
public String getState(){
return this.state;
}
}
}
class Caretaker{
private IFMemento m;
public IFMemento retrieve(){
return this.m;
}
public void save(IFMemento m){
this.m=m;
}
}
interface IFMemento{
}