设计模式的分类和原则整理

//单线程实现单例模式
class Singleton {
    private static Singleton instance;
    
    public Singleton() {};
    
    public static Singleton getInstance (){
        instance = new Singleton();
        
        return instance;
    }
}
 
public class Main {
 
    public static void main(String[] args) {
        Singleton s1 = Singleton.getInstance();
        Singleton s2 = Singleton.getInstance();
        //判断两个实例s1 s2是否为同一个实例
        System.out.println(s1 == s2);
    }
 
}public class Singleton {
 
    //定义一个属性,用来保存Singleton类对象的实例
    private static Singleton instance;
 
    //私有构造器,该类不能被外部类使用new方式实例化
    private Singleton(){
 
    }
 
    //外部通过该方法获取Singleton类的唯一实例
    public static Singleton getInstance(){
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
}

 public static Singleton getInstance() {
        //synchronized加锁同步会降低效率,这里先判断是否为空
        //不为空则不需要加锁,提高程序效率
        if (instance == null) {
            synchronized (Singleton.class) {
                if (instance == null) {
                    instance = new Singleton();
                }
            }
        }
        return instance;
    }

public interface IFactory {
 
    public void createProduct();
}

public class Factory implements IFactory {
 
    @Override
    public void createProduct() {
 
    }
}

//CPU工厂接口
public interface CPUFactory {
    public void createCPU();
}
//IntelCPU工厂
public class IntelCPU implements CPUFactory {
    @Override
    public void createCPU() {
        System.out.println("Intel CPU");
    }
}
//AMDCPU工厂
public class AMDCPU implements CPUFactory {
    @Override
    public void createCPU() {
        System.out.println("AMD CPU");
    }
}
//创建抽象工厂类接口
public interface Provider {
    public CPUFactory createCPUFactory();
}
public class InterCPUFactory implements Provider {
    @Override
    public CPUFactory createCPUFactory() {
        return new InterCPU();
    }
}
public class AMDCPUFactory implements Provider {
    @Override
    public CPUFactory createCPUFactory() {
        return new AMDCPU();
    }
}
public static void main(String[] args) {
        //创建一个生产CPU工厂的工厂
        Provider cpufactory = new InterCPUFactory();
        //通过CPU工厂的工厂创建一个IntelCPU工厂
        CPUFactory intelcpu = cpufactory.createCPUFactory();
        //IntelCPU工厂生产intelCPU
        intelcpu.createCPU();
}

/抽象生产者
public interface Builder {
 
    void buildPartA();
    void buildPartB();
    void buildPartC();
 
    Product buildProduct();
}
//具体生产者
public class ConcreteBuilder implements Builder {
 
    Product product;
 
    @Override
    public void buildPartA() {
 
    }
 
    @Override
    public void buildPartB() {
 
    }
 
    @Override
    public void buildPartC() {
 
    }
 
    @Override
    public Product buildProduct() {
        return product;
    }
}
//产品由各个组件组成
public class Product {
 
    //partA
    //partB
    //partC
}
//指导者,产品生产流程规范
public class Director {
 
    Builder builder;
    //由具体的生产者来生产产品
    public Director(Builder builder) {
        this.builder = builder;
    }
    //生产流程
    public void buildProduct(){
        builder.buildPartA();
        builder.buildPartB();
        builder.buildPartC();
    }
}
public static void main(String[] args) {
        //只需要关心具体建造者,无需关心产品内部构建流程。
        //如果需要其他的复杂产品对象，只需要选择其他的建造者.
        Builder builder = new ConcreteBuilder();
        //把建造者注入指导者
        Director director = new Director(builder);
        //指导者负责流程把控
        director.buildProduct();
        // 建造者返回一个组合好的复杂产品对象
        Product product = builder.buildProduct();
    }

//抽象模板类
public abstract class AbstractSort {
 
    public abstract void sort(int[] array);
    //防止子类覆盖使用final修饰
    public final void printArray(int[] array) {
        sort(array);
        for (int i = 0; i < array.length; i++) {
            System.out.println(array[i]);
        }
    }
}
//具体实现类
public class QuickSort extends AbstractSort {
    @Override
    public void sort(int[] array) {
        //使用快排算法实现
    }
}
public class MergeSort extends AbstractSort {
    @Override
    public void sort(int[] array) {
        //使用归并排序算法实现
    }
}
public static void main(String[] args) {
        int[] arr = {3,5,2,45,243,341,111,543,24};
        //AbstractSort s = new MergeSort();
        AbstractSort s = new QuickSort();
        s.printArray(arr);
    }

//HDMI接口，需要被适配的接口
public interface HDMIPort {
    void workByHDMI();
}
//VGI接口，客户端所期待的接口
public interface VGIPort {
    void workByVGI();
}
//将HDMI接口转换为VGI,这就是适配器
public class HDMIToVGI implements VGIPort{
 
    HDMIPort hdmiPort;
 
    public HDMIToVGI(HDMIPort hdmiPort) {
        this.hdmiPort = hdmiPort;
    }
    //将HDMI接口转换为VGI接口
    @Override
    public void workByVGI() {
        hdmiPort.workByHDMI();
    }
}
 public static void main(String[] args) {
        //定义一个HDMI接口
        HDMIPort hdmiPort = new HDMIPort() {
            @Override
            public void workByHDMI() {
                //hdmi接口工作方式
            }
        };
        //将HDMI接口转换为VGI接口
        VGIPort vgiPort = new HDMIToVGI(hdmiPort);
        //经过转换HDMI接口变成了VGI接口
        vgiPort.workByVGI();
    }

public class CPU {
 
    public void startup(){
        System.out.println("启动CPU");
    }
}
public class Memory {
 
    public void startup(){
        System.out.println("启动内存");
    }
}
public class Disk {
 
    public void startup(){
        System.out.println("启动硬盘");
    }
}
//facade
public class Computer {
 
    CPU cpu;
    Memory memory;
    Disk disk;
 
    public Computer(){
        cpu = new CPU();
        memory = new Memory();
        disk = new Disk();
    }
 
    public void start(){
        cpu.startup();
        memory.startup();
        disk.startup();
    }
}
public static void main(String[] args) {
        Computer computer = new Computer();
        //启动computer是个很复杂的过程,我们并不需要知道其启动各个子系统的加载过程
        //只需要调用computer为各个子系统提供统一的一个接口start()就可以启动computer了
        computer.start();
    }

//InputStream提供的基本方法(Component)
public abstract class InputStream implements Closeable {
 
}
//默认目标实现类(ConcreteComponent)
public class FileInputStream extends InputStream {
 
}
/*装饰实现类（FilterInputStream）一定是继承或实现原始接口(InputStream)的，内部有包含一个原始接口的超类(其实就是某个默认目标实现类)*/
//Decorator
public class FilterInputStream extends InputStream {
    /**
     * The input stream to be filtered.
     */
    protected volatile InputStream in;
 
    protected FilterInputStream(InputStream in) {
        this.in = in;
    }
}
//具体装饰类(ConcreteDecorator)
public class BufferedInputStream extends FilterInputStream {
 
    public BufferedInputStream(InputStream in) {
        this(in, DEFAULT_BUFFER_SIZE);
    }
}
//具体装饰类(ConcreteDecorator)
public class DataInputStream extends FilterInputStream implements DataInput {
 
    public DataInputStream(InputStream in) {
        super(in);
    }
}

public interface Subject {
    //添加观察者
    void attach(Observer o);
    //删除观察者
    void detach(Observer o);
    //通知观察者
    void notifyObservers();
    //发生某事
    void doSomeThings()
}
//观察者
public interface Observer {
 
    void update();
}
public class ConcreteSubject implements Subject {
 
    ArrayList<Observer> observers = new ArrayList<>();
 
    @Override
    public void attach(Observer o) {
        observers.add(o);
    }
 
    @Override
    public void detach(Observer o) {
        observers.remove(o);
    }
 
    @Override
    public void notifyObservers() {
        for (Observer o : observers) {
            o.update();
        }
    }
 
    public void doSomeThings(){
        //doSomeThings
        notifyObservers();//通知观察者
    }
}
//具体观察者
public class ConcreteObserver implements Observer {
    @Override
    public void update() {
        System.out.println("我观察到subject发生了某事");
    }
}
public static void main(String[] args) {
        Subject cs = new ConcreteSubject();
        //添加观察者
        cs.attach(new ConcreteObserver());
        //subject发生了某事，通知观察者
        cs.doSomeThings();
    }

//策略定义算法的接口
public interface Strategy {
    int calculate(int num1,int num2);
}
//具体算法,加法
public class OperationAdd implements Strategy {
    @Override
    public int calculate(int num1, int num2) {
        return num1 + num2;
    }
}
//具体算法,减法
public class OperationSubstract implements Strategy {
    @Override
    public int calculate(int num1, int num2) {
        return num1 - num2;
    }
}
//具体算法,乘法
public class OperationMultiply implements Strategy {
    @Override
    public int calculate(int num1, int num2) {
        return num1 * num2;
    }
}
//具体算法,除法
public class OperationDivide implements Strategy {
    @Override
    public int calculate (int num1, int num2){
        int res = 0;
        try {
            res = num1 / num2;
        }catch (Exception e) {
            e.printStackTrace();
        }
        return res;
    }
}
//上下文
public class Context {
    //持有一个具体策略对象
    private Strategy strategy;
 
    //传入一个具体策略对象
    public Context(Strategy strategy) {
        this.strategy =strategy;
    }
 
    public int calculate(int num1,int num2){
        //调用具体策略对象进行算法运算
        return strategy.calculate(num1,num2);
    }
}
 public static void main(String[] args) {
        //计算 1 + 1
        Context context = new Context(new OperationAdd());
        System.out.println("1 + 1 = " + context.calculate(1,1));
        //计算 1 - 1
        context = new Context(new OperationSubstract());
        System.out.println("1 - 1 = " +context.calculate(1,1));
    }