1.装饰模式

package designPattern;

/**
 * 装饰模式
 * 装饰模式在不改变原有类结构的情况下向现有对象添加新功能
 * 使用一个会变颜色的圆圈来举例
 */
public class DecoratingMode {
    public static void main(String[] args) {
        Shape circle = new Circle();
        Shape square = new Square();
        ColorDecorator colorDecorator = new ColorDecorator(circle);
        colorDecorator.draw();
        ColorDecorator colorDecorator1 = new ColorDecorator(square);
        colorDecorator1.draw();
    }
}

/**
 * 形状接口
 */
interface Shape {
    void print();
}

class Circle implements Shape {
    @Override
    public void print() {
        System.out.println("i am circle");
    }
}

class Square implements Shape {
    @Override
    public void print() {
        System.out.println("i am square");
    }
}

/**
 * 装饰器抽象类
 */
abstract class AbstractDecorator {
    protected Shape shape;

    public abstract void draw();
}

/**
 * 为形状装饰蓝色的装饰器
 */
class ColorDecorator extends AbstractDecorator {
    public ColorDecorator(Shape shape) {
        this.shape = shape;
    }

    @Override
    public void draw() {
        shape.print();
        setColor();
    }

    public void setColor() {
        System.out.println("Color is Blue");
    }
}

2.外观模式

package designPattern;

/**
 * 外观模式
 * 外观模式（Facade Pattern）隐藏系统的复杂性，并向客户端提供了一个客户端可以访问系统的接口
 */
public class AppearanceMode {
    public static void main(String[] args) {
        OperationInterface operationInterface = new OperationInterface();
        operationInterface.printCircle();
        operationInterface.printSquare();
    }
}

/**
 * 形状接口
 */
interface Shape {
    void print();
}

class Circle implements Shape {
    @Override
    public void print() {
        System.out.println("i am circle");
    }
}

class Square implements Shape {
    @Override
    public void print() {
        System.out.println("i am square");
    }
}

/**
 * 包装类，隐藏内部结构，向用户提供使用接口
 */
class OperationInterface {
    private Shape circle;
    private Shape square;

    public OperationInterface() {
        circle = new Circle();
        square = new Square();
    }

    public void printCircle() {
        circle.print();
    }

    public void printSquare() {
        square.print();
    }
}

3.代理模式

package designPattern;

/**
 * 代理模式
 * 在代理模式（Proxy Pattern）中，一个类代表另一个类的功能。这种类型的设计模式属于结构型模式。
 * 在代理模式中，我们创建具有现有对象的对象，以便向外界提供功能接口
 */
public class ProxyPattern {
    public static void main(String[] args) {
        ProxyImage proxyImage = new ProxyImage("test.jpg");
        //第一次显示需要加载图片
        proxyImage.display();
        //第二次不需要加载
        proxyImage.display();
    }
}

/**
 * 图像接口
 */
interface Image {
    void display();
}

/**
 * 真实的照片类
 */
class RealImage implements Image {
    private String fileName;

    public RealImage(String fileName) {
        this.fileName = fileName;
        loadFromDisk(fileName);
    }

    @Override
    public void display() {
        System.out.println("Displaying " + fileName);
    }

    private void loadFromDisk(String fileName) {
        System.out.println("Loading " + fileName);
    }
}

/**
 * 代理照片类
 */
class ProxyImage implements Image {

    private RealImage realImage;
    private String fileName;

    public ProxyImage(String fileName) {
        this.fileName = fileName;
    }

    @Override
    public void display() {
        if (realImage == null) {
            realImage = new RealImage(fileName);
        }
        realImage.display();
    }
}