一、面向对象基础

先了解一下面向对象与面向过程的区别？

1、面向对象的基本概念

2、面向对象的三大特性

1.封装

方法就可以理解成封装 属性的封装就是将访问权限设置成私有访问时则是通过get()和set()方法

2.继承

3.多态

绑定(动态绑定----运行时进行的,静态绑定----编译时进行的)

3、面向对象设计的原则(五大原则)

4、面向对象分析

5、面向对象设计

6、面向对象测试

杂题

二、UML

1、事物

2、关系

3、UML中的图

1、类图

2、对象图

3、用例图

4、交互图

1、序列图

2、通信图

5、状态图

6、活动图

7、构件图(组件图)

8、部署图

9、UML汇总

杂题

三、设计模式(其存在就类似于框架)

1、设计模式的要素

2、创建型设计模式

先引入简单工厂模式：简单工厂模式--》存在的问题--》违反了开放封闭原则。

public class SimpleFactory {
    public static void main(String[] args) {
        Product productA = Factory.createProduct("A");
        productA.info();
        
        Product productB = Factory.createProduct("B");
    }
}

abstract class Product {
    public abstract void info();
}

class Factory {
    public static Product createProduct(String type) {
        Product product = null;
        
        switch (type) {
            case "A":
                product = new ProductA();
                break;
            case "B":
                product = new ProductB();
                break;
            default:
                System.out.println("没有 " + type + " 类型的产品！");
                break;
        }
        
        return product;
    }
}

class ProductA extends Product {
    
    @Override
    public void info() {
        System.out.println("产品的信息：A");
    }
}

class ProductB extends Product {

    @Override
    public void info() {
        System.out.println("产品的信息：B");
    }
}

1、工厂方法模式（Factory Method）（一对一）

public class FactoryMethod {
    public static void main(String[] args) {
        Factory factoryA = new FactoryA();
        // 父类 对象名 = new 子类();

        Product productA = factoryA.createProduct();
        // Product productA = new ProductA();
        productA.info();

        Factory factoryB = new FactoryB();

        Product productB = factoryB.createProduct();
        productB.info();
    }
}

// class Factory
interface Factory {
    public Product createProduct();
}

class FactoryA implements Factory {

    @Override
    public Product createProduct() {
        return new ProductA();
    }
}

class FactoryB implements Factory {

    @Override
    public Product createProduct() {
        return new ProductB();
    }
}

// abstract class Product
interface Product {
    // public abstract void info();
    public void info();
}

// class ProductA extends Product
class ProductA implements Product {

    @Override
    public void info() {
        System.out.println("产品的信息：A");
    }
}

// class ProductB extends Product
class ProductB implements Product {

    @Override
    public void info() {
        System.out.println("产品的信息：B");
    }
}

2、抽象工厂模式（Abstract Factory）（一对多）

public class AbstractFactory {
    public static void main(String[] args) {
        Factory factory1 = new Factory1();

        ProductA productA = factory1.createProductA();
        productA.info();

        Factory factory2 = new Factory2();

        ProductB productB = factory2.createProductB();
        productB.info();
    }
}

interface Factory {
    public ProductA createProductA();
    public ProductB createProductB();
}

class Factory1 implements Factory {

    @Override
    public ProductA createProductA() {
        return new ProductA1();
    }

    @Override
    public ProductB createProductB() {
        return new ProductB1();
    }
}

class Factory2 implements Factory {

    @Override
    public ProductA createProductA() {
        return new ProductA2();
    }

    @Override
    public ProductB createProductB() {
        return new ProductB2();
    }
}

interface ProductA {
    public void info();
}

class ProductA1 implements ProductA {

    @Override
    public void info() {
        System.out.println("产品的信息：A1");
    }
}

class ProductA2 implements ProductA {

    @Override
    public void info() {
        System.out.println("产品的信息：A2");
    }
}

interface ProductB {
    public void info();
}

class ProductB1 implements ProductB {

    @Override
    public void info() {
        System.out.println("产品的信息：B1");
    }
}

class ProductB2 implements ProductB {

    @Override
    public void info() {
        System.out.println("产品的信息：B2");
    }
}

3、生成器模式（Builder）

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Director director = new Director();

        Builder builder1 = new Builder1();
        director.Construct(builder1);
        Product product1 = builder1.getResult();
        product1.show();

        Builder builder2 = new Builder2();
        director.Construct(builder2);
        Product product2 = builder2.getResult();
        product2.show();
    }
}

class Director {
    public void Construct(Builder builder) {
        builder.BuildPart();
    }
}

abstract class Builder {
    public abstract void BuildPart();
    public abstract Product getResult();
}

class Builder1 extends Builder {
    Product product = new Product();

    @Override
    public void BuildPart() {
        product.Add("A");
        product.Add("B");
        product.Add("C");
        product.Add("D");
        product.Add("E");
        product.Add("F");
    }

    @Override
    public Product getResult() {
        return product;
    }
}

class Builder2 extends Builder {
    Product product = new Product();

    @Override
    public void BuildPart() {
        product.Add("A");
        product.Add("B");
        product.Add("C");
    }

    @Override
    public Product getResult() {
        return product;
    }
}

class Product {
    List<String> parts = new ArrayList<String>();

    public void Add(String part) {
        parts.add(part);
    }

    public void show() {
        System.out.print("产品的组成：");
        for (String s : parts)
            System.out.print(s + " ");

        System.out.print("\n");
    }
}

4、原型模式（Prototype）

public class Main {
    public static void main(String[] args) {
        Product product1 = new Product(2022, 5.28);
        System.out.println(product1.getId() + " " + product1.getPrice());

        // Product product2 = new Product(2022, 5.28);
        Product product2 = (Product) product1.Clone();
        System.out.println(product2.getId() + " " + product2.getPrice());

        Product product3 = (Product) product1.Clone();
        System.out.println(product3.getId() + " " + product3.getPrice());
    }
}

interface Prototype {
    public Object Clone();
}

class Product implements Prototype {
    private int id;
    private double price;

    public Product() {}

    public Product(int id, double price) {
        this.id = id;
        this.price = price;
    }

    public int getId() {
        return id;
    }

    public double getPrice() {
        return price;
    }

    @Override
    public Object Clone() {
        Product object = new Product();
        object.id = this.id;
        object.price = this.price;

        return object;
    }
}

5、单例模式（singleton）

public class SingletonPattern {
    public static void main(String[] args) {
        // Singleton singleton1 = new Singleton();

        Singleton singleton1 = Singleton.getInstance();
        Singleton singleton2 = Singleton.getInstance();
        Singleton singleton3 = Singleton.getInstance();

        System.out.println(singleton1.getNumber() + " " + singleton2.getNumber() + " " + singleton3.getNumber());

        singleton1.setNumber(528);
        System.out.println(singleton1.getNumber() + " " + singleton2.getNumber() + " " + singleton3.getNumber());

    }
}

class Singleton {
    private int number = 2022;

    public void setNumber(int number) {
        this.number = number;
    }

    public int getNumber() {
        return number;
    }

    private static Singleton instance = new Singleton();

    private Singleton() {}

    public static Singleton getInstance() {
        return instance;
    }
}

3、结构型设计模式

1、适配器（Adapter）

public class AdapterPattern {
    public static void main(String[] args) {
        USB usb = new Adapter();
        usb.Request();
    }
}

class USB {
    public void Request() {
        System.out.println("USB数据线");
    }
}

class Adapter extends USB {
    private TypeC typeC = new TypeC();

    @Override
    public void Request() {
        typeC.SpecificRequest();
    }
}

class TypeC {
    public void SpecificRequest() {
        System.out.println("Type-C数据线");
    }
}

2、桥接模式（bridge）

public class BridgePattern {
    public static void main(String[] args) {
        Product productA1 = new ProductA();
        Product productA2 = new ProductA();
        Color red = new Red();

        productA1.setName("产品A1");
        productA1.setColor(red);
        productA1.Operation();


        Blue blue = new Blue();
        productA2.setName("产品A2");
        productA2.setColor(blue);
        productA2.Operation();
    }
}

abstract class Product {
    private String name;
    protected Color color;

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setColor(Color color) {
        this.color = color;
    }

    public abstract void Operation();
}

class ProductA extends Product {

    @Override
    public void Operation() {
        color.OperationImp(this.getName());
    }
}

interface Color {
    public void OperationImp(String name);
}

class Red implements Color {

    @Override
    public void OperationImp(String name) {
        System.out.println(name + "：红色");
    }
}

class Blue implements Color {

    @Override
    public void OperationImp(String name) {
        System.out.println(name + "：蓝色");
    }
}

3、组合模式（composite）

import java.util.*;

public class CompositePattern {
    public static void main(String[] args) {
        // 父类名 对象名 = new 子类名();
        AbstractFile root = new Folder("root");

        AbstractFile folderA = new Folder("folderA");
        AbstractFile folderB = new Folder("folderB");

        AbstractFile fileC = new File("fileC");
        AbstractFile fileD = new File("fileD");
        AbstractFile fileE = new File("fileE");

        root.Add(folderA);
        root.Add(folderB);
        root.Add(fileC);

        folderA.Add(fileD);
        folderA.Add(fileE);

        print(root);
    }

    static void print(AbstractFile file) {
        file.printName();

        List<AbstractFile> childrenList = file.getChildren();
        if (childrenList == null) return;

        // for (对象类型 对象名 : 遍历对象)
        for (AbstractFile children : childrenList) {
            // children.printName();
            print(children);
        }
    }
}

abstract class AbstractFile {
    protected String name;

    public void printName() {
        System.out.println(name);
    }

    public abstract boolean Add(AbstractFile file);
    public abstract boolean Remove(AbstractFile file);
    public abstract List<AbstractFile> getChildren();
}

class Folder extends AbstractFile {
    private List<AbstractFile> childrenList = new ArrayList<AbstractFile>();

    public Folder(String name) {
        this.name = name;
    }

    @Override
    public boolean Add(AbstractFile file) {
        return childrenList.add(file);
    }

    @Override
    public boolean Remove(AbstractFile file) {
        return childrenList.remove(file);
    }

    @Override
    public List<AbstractFile> getChildren() {
        return childrenList;
    }
}

class File extends AbstractFile {
    public File(String name) {
        this.name = name;
    }

    @Override
    public boolean Add(AbstractFile file) {
        return false;
    }

    @Override
    public boolean Remove(AbstractFile file) {
        return false;
    }

    @Override
    public List<AbstractFile> getChildren() {
        return null;
    }
}

4、装饰器模式（decorator）

public class DecoratorPattern {
    public static void main(String[] args) {
        Person zhangsan = new Student("张三");
        zhangsan = new DecoratorA(zhangsan);
        zhangsan = new DecoratorB(zhangsan);
        zhangsan.Operation();

        System.out.println("\n=====我是分割线=====");

        // 对象链
        Person lisi = new DecoratorB(new DecoratorA(new Student("李四")));
    }
}

abstract class Decorator extends Person {
    protected Person person;
}

class DecoratorA extends Decorator {
    public DecoratorA(Person person) {
        this.person = person;
    }

    @Override
    public void Operation() { // 职责
        person.Operation(); // 原本的职责
        System.out.print("写作业 ");
    }
}

class DecoratorB extends Decorator {
    public DecoratorB(Person person) {
        this.person = person;
    }

    @Override
    public void Operation() { // 职责
        person.Operation(); // 原本的职责
        System.out.print("考试 ");
    }
}

abstract class Person {
    protected String name;

    public abstract void Operation(); // 职责
}

class Student extends Person {
    public Student(String name) {
        this.name = name;
    }

    @Override
    public void Operation() {
        System.out.print(name + "的职责：学习 ");
    }
}

5、外观模式（facade）

public class FacadePattern {
    public static void main(String[] args) {
        Facade facade = new Facade();

        facade.methodA();
        facade.methodB();
        facade.methodC();
    }
}

class Facade {
    SubSystemOne subSystemOne;
    SubSystemTwo subSystemTwo;
    SubSystemThree subSystemThree;

    public Facade() {
        subSystemOne = new SubSystemOne();
        subSystemTwo = new SubSystemTwo();
        subSystemThree = new SubSystemThree();
    }

    public void methodA() {
        subSystemOne.methodOne();
    }

    public void methodB() {
        subSystemTwo.methodTwo();
    }

    public void methodC() {
        subSystemThree.methodThree();
    }
}

class SubSystemOne {
    public void methodOne() {
        System.out.println("执行子系统一的功能");
    }
}

class SubSystemTwo {
    public void methodTwo() {
        System.out.println("执行子系统二的功能");
    }
}

class SubSystemThree {
    public void methodThree() {
        System.out.println("执行子系统三的功能");
    }
}

6、享元模式（flyweight）

import java.util.*;

public class FlyWeightPattern {
    public static void main(String[] args) {
        ShapeFactory factory = new ShapeFactory();

        Random random = new Random();
        String[] colors = {"red", "blue", "green", "white", "black"};

        for (int i = 1; i <= 100; i ++ ) {
            int x = random.nextInt(colors.length); // [0 ~ 4]
            Shape shape = factory.getShape(colors[x]);

            System.out.print("第" + i + "个圆：");
            shape.draw(random.nextInt(2022), random.nextInt(528));
        }
    }
}

class ShapeFactory {
    private Map<String, Shape> map = new HashMap<String, Shape>();

    public Shape getShape(String key) {
        if (!map.containsKey(key)) {
            map.put(key, new Circle(key));
            System.out.println("create color：" + key + " circle");
        }

        return map.get(key);
    }
}

abstract class Shape {
    protected String color;

    public abstract void draw(int x, int y);
}

class Circle extends Shape {
    public Circle(String color) {
        this.color = color;
    }

    @Override
    public void draw(int x, int y) {
        System.out.println("draw a color：" + color + " circle x：" + x + " y：" + y);
    }
}

7、代理模式（proxy）

public class ProxyPattern {
    public static void main(String[] args) {
        RealSubject realSubject = new RealSubject();
        Proxy proxy = new Proxy(realSubject);

        proxy.buy();
    }
}

interface Subject {
    public void buy();
}

class Proxy implements Subject {
    protected RealSubject realSubject;

    public Proxy(RealSubject realSubject) {
        this.realSubject = realSubject;
    }

    @Override
    public void buy() {
        System.out.println("办理购买前的手续");
        realSubject.buy(); // 付钱
        System.out.println("办理购买后的手续");
    }
}

class RealSubject implements Subject {

    @Override
    public void buy() {
        System.out.println("付钱");
    }
}

4、行为设计模式

1、责任链（chain of responsibility）

public class ChainOfResponsibilityPattern {
    public static void main(String[] args) {
        Handler fudaoyuan = new FuDaoYuan();
        Handler yuanzhang = new YuanZhang();
        Handler xiaozhang = new XiaoZhang();

        fudaoyuan.setNext(yuanzhang);
        yuanzhang.setNext(xiaozhang);

        fudaoyuan.HandlerRequest(31);
    }
}

abstract class Handler {
    protected Handler next;

    public void setNext(Handler next) {
        this.next = next;
    }

    public abstract void HandlerRequest(int request);
}

class FuDaoYuan extends Handler { // <= 7 审批

    @Override
    public void HandlerRequest(int request) {
        if (request <= 7) {
            System.out.println("辅导员审批通过");
        } else {
            if (next != null) {
                next.HandlerRequest(request);
            } else {
                System.out.println("无法审批");
            }
        }
    }
}

class YuanZhang extends Handler { // <= 15 审批

    @Override
    public void HandlerRequest(int request) {
        if (request <= 15) {
            System.out.println("院长审批通过");
        } else {
            if (next != null) {
                next.HandlerRequest(request);
            } else {
                System.out.println("无法审批");
            }
        }
    }
}

class XiaoZhang extends Handler { // <= 30 审批

    @Override
    public void HandlerRequest(int request) {
        if (request <= 30) {
            System.out.println("校长审批通过");
        } else {
            if (next != null) {
                next.HandlerRequest(request);
            } else {
                System.out.println("无法审批");
            }
        }
    }
}

2、命令模式（command）

public class CommandPattern {
    public static void main(String[] args) {
        Tv tv = new Tv(); // 接收者 对象 电视机

        Command onCommand = new OnCommand(tv); // 命令对象 开机命令
        Command offCommand = new OffCommand(tv); // 命令对象 关机命令

        Invoker invoker = new Invoker(); // 请求者
        invoker.setCommand(onCommand); // 给请求者设置 开机 命令
        invoker.call(); // 请求者去请求命令

        System.out.println("========================================");

        invoker.setCommand(offCommand); // 给请求者设置 关机命令
        invoker.call(); // 请求者去请求命令
    }
}

class Invoker { // 请求者
    private Command command; // 命令

    public void setCommand(Command command) { // 设置请求者 的 请求的命令
        this.command = command;
    }

    public void call() { // 调用
        command.Execute();
    }
}

interface Command { // 命令接口
    public void Execute(); // 执行命令
}

class OnCommand implements Command { // 开机命令
    private Tv tv;

    public OnCommand(Tv tv) {
        this.tv = tv;
    }

    @Override
    public void Execute() {
        tv.OnAction();
    }
}

class OffCommand implements Command { // 关机命令
    private Tv tv;

    public OffCommand(Tv tv) {
        this.tv = tv;
    }

    @Override
    public void Execute() {
        tv.OffAction();
    }
}

class Tv { // 接收者 电视机
    public void OnAction() { // 开机行为
        System.out.println("电视机开机了...");
    }

    public void OffAction() { // 关机行为
        System.out.println("电视机关机了...");
    }
}

3、解释器模式（interpreter）

import java.util.*;

public class InterpreterPattern {
    public static void main(String[] args) {
        Context context = new Context();

        context.check("A区的开发人员");
        context.check("B区的调试人员");
        context.check("C区的测试人员");

        System.out.println("==========");

        context.check("D区的程序员");
        context.check("D区的测试员");
        context.check("A区的程序员");
    }
}

class Context {
    private String[] regions = {"A区", "B区", "C区"};
    private String[] persons = {"开发人员", "测试人员", "调试人员"};

    private NonterminalExprssion nonterminal;

    public Context() {
        TerminalExpression region = new TerminalExpression(regions);
        TerminalExpression person = new TerminalExpression(persons);
        nonterminal = new NonterminalExprssion(region, person);
    }

    public void check(String info) {
        boolean bool = nonterminal.Interpret(info);
        if (bool) {
            System.out.println("识别成功");
        } else {
            System.out.println("识别失败");
        }
    }
}

interface Expression {
    public boolean Interpret(String info);
}

class NonterminalExprssion implements Expression {
    private TerminalExpression region;
    private TerminalExpression person;

    public NonterminalExprssion(TerminalExpression region, TerminalExpression person) {
        this.region = region;
        this.person = person;
    }

    @Override
    public boolean Interpret(String info) {
        String[] str = info.split("的");
        // B区的调试人员 --> str = {"B区", "调试人员"}

        return region.Interpret(str[0]) && person.Interpret(str[1]);
    }
}

class TerminalExpression implements Expression {
    private Set<String> set = new HashSet<>();

    public TerminalExpression(String[] data) {
        // for (遍历对象类型 对象名 : 遍历对象)
        for (String str : data) {
            set.add(str);
        }
    }

    @Override
    public boolean Interpret(String info) {
        return set.contains(info);
    }
}

4、迭代器模式（iterator）

import java.util.*;

public class IteratorPattern {
    public static void main(String[] args) {
        BookAggregate bookAggregate = new BookAggregate();

        String[] books = {"数据结构", "操作系统", "计算机网络", "计算机组成原理"};
        double[] prices = {10.24, 20.48, 40.96, 81.92};

        for (int i = 0; i < 4; i ++ ) {
            bookAggregate.Add(new Book(books[i], prices[i]));
        }

        Iterator bookIterator = bookAggregate.CreateIterator();
        while (bookIterator.hasNext()) {
            Book book = (Book) bookIterator.next();
            System.out.println(book.getName() + " " + book.getPrice());
        }
    }
}

interface Iterator {
    public boolean hasNext();
    public Object next();
}

class BookIterator implements Iterator {
    private int index;
    private BookAggregate bookAggregate;

    public BookIterator(BookAggregate bookAggregate) {
        this.index = 0;
        this.bookAggregate = bookAggregate;
    }

    @Override
    public boolean hasNext() {
        if (index < bookAggregate.getSize()) {
            return true;
        } else {
            return false;
        }
    }

    @Override
    public Object next() {
        Object obj = bookAggregate.get(index);
        index ++ ;

        return obj;
    }
}

interface Aggregate {
    public Iterator CreateIterator();
}

class BookAggregate implements Aggregate {
    private List<Book> list = new ArrayList<Book>();

    public void Add(Book book) {
        list.add(book);
    }

    public Book get(int index) {
        return list.get(index);
    }

    public int getSize() {
        return list.size();
    }

    @Override
    public Iterator CreateIterator() {
        return new BookIterator(this);
    }
}


class Book {
    private String name;
    private double price;

    public Book(String name, double price) {
        this.name = name;
        this.price = price;
    }

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }
}

5、中介者模式（mediator）

public class MediatorPattern {
    public static void main(String[] args) {
        ConcreteMediator mediator = new ConcreteMediator();

        Colleague1 colleague1 = new Colleague1(mediator);
        Colleague2 colleague2 = new Colleague2(mediator);

        mediator.setColleague1(colleague1);
        mediator.setColleague2(colleague2);

        colleague1.sendMessage("软考加油");

        colleague2.sendMessage("祝大家软考顺利通过！");
    }
}


abstract class Colleague {
    protected Mediator mediator;
}

class Colleague1 extends Colleague {
    public Colleague1(Mediator mediator) {
        this.mediator = mediator;
    }

    public void sendMessage(String message) {
        mediator.sendMessage(message, this);
    }

    public void Notify(String message) {
        System.out.println("同事1收到消息：" + message);
    }
}

class Colleague2 extends Colleague {
    public Colleague2(Mediator mediator) {
        this.mediator = mediator;
    }

    public void sendMessage(String message) {
        mediator.sendMessage(message, this);
    }

    public void Notify(String message) {
        System.out.println("同事2收到消息：" + message);
    }
}

abstract class Mediator {
    public abstract void sendMessage(String message, Colleague colleague);
}

class ConcreteMediator extends Mediator {
    private Colleague1 colleague1;
    private Colleague2 colleague2;

    public void setColleague1(Colleague1 colleague1) {
        this.colleague1 = colleague1;
    }

    public void setColleague2(Colleague2 colleague2) {
        this.colleague2 = colleague2;
    }

    public void sendMessage(String message, Colleague colleague) {
        if (colleague == colleague1) {
            colleague2.Notify(message); // 让同事2收到消息
        } else {
            colleague1.Notify(message); // 让同事1收到消息
        }
    }
}

6、备忘录模式（memento）

import java.util.*;

public class MementoPattern {
    public static void main(String[] args) {
        Caretaker caretaker = new Caretaker();
        Originator originator = new Originator();

        originator.setState("1024");
        Memento backup1 = originator.createMemento();
        caretaker.addMemento(backup1);

        originator.setState("2048");
        Memento backup2 = originator.createMemento();
        caretaker.addMemento(backup2);

        originator.setState("4096");
        Memento backup3 = originator.createMemento();
        caretaker.addMemento(backup3);

        System.out.println(originator.getState());

        caretaker.showMemento();

        Memento memento1 = caretaker.getMemento(2);
        originator.setMemento(memento1);

        System.out.println("根据第2次备份还原之后的状态为：" + originator.getState());
    }
}

class Originator { // 原发器
    private String state;

    public void setState(String state) {
        this.state = state;
    }

    public String getState() {
        return state;
    }

    public Memento createMemento() {
        return new Memento(state);
    }

    public void setMemento(Memento memento) {
        state = memento.getState();
    }
}

class Memento { // 备忘录
    private String state;

    public Memento(String state) {
        this.state = state;
    }

    public String getState() {
        return state;
    }
}

class Caretaker { // 管理者
    private List<Memento> mementoList = new ArrayList<>();

    public void addMemento(Memento memento) {
        mementoList.add(memento);
    }

    public Memento getMemento(int index) {
        // 判断参数是否合法
        if (index >= 1 && index <= mementoList.size()) {
            return mementoList.get(index - 1);
        }

        return null;
    }

    public void showMemento() {
        int cnt = 1;
        // for (遍历对象类型 对象名 : 遍历对象)
        for (Memento memento : mementoList) {
            System.out.println("第" + cnt + "次备份，状态为：" + memento.getState());

            cnt ++ ;
        }
    }
}

7、观察者模式（observer）--》就像up主更新状态，所关注的用户都会收到通知

import java.util.*;

public class ObserverPattern {
    public static void main(String[] args) {
        Subject subjectA = new ConcreteSubject("目标A");

        Observer observerB = new ConcreteObserver("张三", subjectA);
        Observer observerC = new ConcreteObserver("李四", subjectA);
        Observer observerD = new ConcreteObserver("王五", subjectA);

        subjectA.setState("更新了");

        System.out.println("======================================");

        subjectA.Detach(observerD);

        subjectA.setState("停更了");
    }
}

interface Subject { // 目标
    public void Attach(Observer observer); // 添加观察者
    public void Detach(Observer observer); // 删除观察者
    public void Notify(); // 状态改变后 通知所有观察者

    public void setState(String state); // 设置状态（改变状态）
    public String getState(); // 获取状态
}

class ConcreteSubject implements Subject {
    private String name;
    private String state;

    private List<Observer> observerList;

    public ConcreteSubject(String name) {
        state = "未更新";
        this.name = name;

        observerList = new ArrayList<Observer>();
    }

    public void setState(String state) {
        this.state = state;

        System.out.println(name + "的状态发生变化，变化后的状态为：" + state);
        Notify();
    }

    public String getState() {
        return state;
    }

    public void Attach(Observer observer) {
        observerList.add(observer);
    }

    public void Detach(Observer observer) {
        observerList.remove(observer);
    }

    public void Notify() {
        // for (遍历对象类型 对象名 : 遍历对象)
        for (Observer observer : observerList) {
            observer.update();
        }
    }
}

interface Observer { // 观察者接口
    public void update(); // 收到通知 更新观察者的状态
}

class ConcreteObserver implements Observer {
    private String name;
    private String state;

    private Subject subject;

    public ConcreteObserver(String name, Subject subject) {
        this.name = name;

        this.subject = subject;
        subject.Attach(this);

        state = subject.getState();
    }

    @Override
    public void update() {
        System.out.println(name + "收到通知");
        state = subject.getState(); // 让当前观察者的状态 和 改变了状态之后的目标的状态保持一致

        System.out.println(name + "改变后的状态为：" + state);
    }
}

8、状态模式（state）--》贩卖机是否有货之间的转换

public class StatePattern {
    public static void main(String[] args) {
        Context context = new Context(); // count：3

        System.out.println(context.getState());

        context.Request(); // 购买一个饮料 count = 2
        context.Request(); // 购买一个饮料 count = 1
        context.Request(); // 购买一个饮料 count = 0

        System.out.println(context.getState());

        context.Request(); // 无货 等待补货 补货成功 count = 5

        System.out.println(context.getState());

        context.Request(); // 购买一个饮料 count = 4
        System.out.println(context.getCount());

    }
}

class Context { // 贩卖机
    private int count;

    private State state;

    public Context() {
        count = 3;
        state = new StateA();
    }

    public int getCount() {
        return count;
    }

    public void setCount(int count) {
        this.count = count;
    }

    public State getState() {
        return state;
    }

    public void setState(State state) {
        this.state = state;
    }

    public void Request() { // 购买一个饮料
        state.Handle(this);
    }

}

interface State {
    public void Handle(Context context);
}

class StateA implements State { // 有货

    @Override
    public void Handle(Context context) {
        int count = context.getCount();

        if (count >= 1) {
            System.out.println("购买成功！");
            context.setCount(count - 1);

            if (context.getCount() == 0) {
                context.setState(new StateB());
            }
        } else {
            System.out.println("购买失败！");
        }
    }
}

class StateB implements State { // 无货

    @Override
    public void Handle(Context context) {
        int count = context.getCount();

        if (count == 0) {
            System.out.println("购买失败！等待补货");

            context.setCount(5);
            System.out.println("补货成功，请重新购买");
            context.setState(new StateA());
        }
    }
}

9、策略模式（strategy）

public class StrategyPattern {
    public static void main(String[] args) {
        Strategy add = new AddStrategy();
        Strategy subtraction = new SubtractionStrategy();
        Strategy multiply = new MultiplyStrategy();

        OperationContext context = new OperationContext(add);
        context.Operation(2022, 528);

        context = new OperationContext(subtraction);
        context.Operation(2022, 528);

        context = new OperationContext(multiply);
        context.Operation(2022, 528);
    }
}

class OperationContext {
    private Strategy strategy;

    public OperationContext(Strategy strategy) {
        this.strategy = strategy;
    }

    public void Operation(int a, int b) {
        strategy.TwoNumberOperation(a, b);
    }
}

interface Strategy {
    public void TwoNumberOperation(int a, int b);
}

class AddStrategy implements Strategy {

    @Override
    public void TwoNumberOperation(int a, int b) {
        System.out.println(a + b);
    }
}

class SubtractionStrategy implements Strategy {

    @Override
    public void TwoNumberOperation(int a, int b) {
        System.out.println(a - b);
    }
}

class MultiplyStrategy implements Strategy {

    @Override
    public void TwoNumberOperation(int a, int b) {
        System.out.println(a * b);
    }
}

10、模板方法模式（template method）

public class TemplateMethodPattern {
    public static void main(String[] args) {
        // 父类名 对象名 = new 子类名();

        Person student = new Student();
        Person teacher = new Teacher();

        student.TemplateMethod();

        System.out.println("=====我是分割线=====");

        teacher.TemplateMethod();
    }
}

abstract class Person {
    public void TemplateMethod() {
        System.out.println("上课 去教室"); // 1
        PrimitiveOperation1(); // 2
        System.out.println("下课 离开教室"); // 3
        PrimitiveOperation2(); // 4
    }

    public abstract void PrimitiveOperation1(); // 原语操作 1 ：上课过程 学生 听课…… 老师 讲课
    public abstract void PrimitiveOperation2(); // 原语操作 2 ：作业     学生 写作业 提交作业…… 老师 批改作业 打分数
}

class Student extends Person {

    @Override
    public void PrimitiveOperation1() {
        System.out.println("学生：听课 学习 做笔记 提出问题");
    }

    @Override
    public void PrimitiveOperation2() {
        System.out.println("学生：写作业 提交作业");
    }
}

class Teacher extends Person {

    @Override
    public void PrimitiveOperation1() {
        System.out.println("老师：上课 讲课 解答问题 布置作业");
    }

    @Override
    public void PrimitiveOperation2() {
        System.out.println("老师：批改作业 打分数");
    }
}

11、访问者模式（visitor）

import java.util.*;

public class VisitorPattern {
    public static void main(String[] args) {
        PersonStructure structure = new PersonStructure();

        Visitor1 visitor1 = new Visitor1();
        System.out.println("访问者1的访问记录：");
        structure.Accept(visitor1);
        System.out.println("学生年龄的总和：" + visitor1.getStudentAgeSum() + " 老师年龄的总和：" + visitor1.getTeacherAgeSum());

        System.out.println("=========================================");

        Visitor2 visitor2 = new Visitor2();
        System.out.println("访问者2的访问记录：");
        structure.Accept(visitor2);
        System.out.println("学生的最高成绩：" + visitor2.getMaxScore() + " 老师的最高工龄：" + visitor2.getMaxWorkYear());
    }
}

interface Visitor {
    public void visitStudent(Student student); // 访问学生
    public void visitTeacher(Teacher teacher); // 访问老师
}

class Visitor1 implements Visitor { // 访问者1 分别统计学生和老师的年龄总和
    private int studentAgeSum = 0;
    private int teacherAgeSum = 0;

    public int getStudentAgeSum() {
        return studentAgeSum;
    }

    public int getTeacherAgeSum() {
        return teacherAgeSum;
    }

    @Override
    public void visitStudent(Student student) {
        System.out.println("访问者1访问学生：" + student.getName() + " 年龄：" + student.getAge());
        studentAgeSum += student.getAge();
    }

    @Override
    public void visitTeacher(Teacher teacher) {
        System.out.println("访问者1访问老师：" + teacher.getName() + " 年龄：" + teacher.getAge());
        teacherAgeSum += teacher.getAge();
    }
}

class Visitor2 implements Visitor { // 访问者2 分别求出 学生的最高成绩 以及 老师的最高工龄
    private int maxScore = -1;
    private int maxWorkYear = -1;

    public int getMaxScore() {
        return maxScore;
    }

    public int getMaxWorkYear() {
        return maxWorkYear;
    }

    @Override
    public void visitStudent(Student student) {
        System.out.println("访问者2访问学生：" + student.getName() + " 成绩：" + student.getScore());
        maxScore = Math.max(maxScore, student.getScore());
    }

    @Override
    public void visitTeacher(Teacher teacher) {
        System.out.println("访问者2访问老师：" + teacher.getName() + " 工龄：" + teacher.getWorkYear());
        maxWorkYear = Math.max(maxWorkYear, teacher.getWorkYear());
    }
}

class PersonStructure {
    private List<Person> personList = new ArrayList<Person>();

    public PersonStructure() {
        personList.add(new Student("张三", 20, 70));
        personList.add(new Student("李四", 21, 80));
        personList.add(new Student("王五", 22, 90));

        personList.add(new Teacher("李老师", 26, 3));
        personList.add(new Teacher("陈老师", 27, 4));
        personList.add(new Teacher("刘老师", 28, 5));
    }

    public void Accept(Visitor visitor) {
        // for (遍历对象类型 对象名 : 遍历对象)
        for (Person person : personList) {
            person.Accept(visitor);
        }
    }
}

abstract class Person {
    private String name;
    private int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public abstract void Accept(Visitor visitor);
}

class Student extends Person {
    private int score;

    public Student(String name, int age, int score) {
        super(name, age);

        this.score = score;
    }

    public int getScore() {
        return score;
    }

    @Override
    public void Accept(Visitor visitor) {
        visitor.visitStudent(this);
    }
}

class Teacher extends Person {
    private int workYear;

    public Teacher(String name, int age, int workYear) {
        super(name, age);

        this.workYear = workYear;
    }

    public int getWorkYear() {
        return workYear;
    }

    @Override
    public void Accept(Visitor visitor) {
        visitor.visitTeacher(this);
    }
}

5、总结