📅  最后修改于: 2020-12-21 02:01:26             🧑  作者: Mango
装饰器模式允许用户向现有对象添加新功能,而无需更改其结构。这种设计模式属于结构模式,因为该模式充当现有类的包装。
此模式创建一个包装原始类的装饰器类,并提供其他功能,以保持类方法的签名完整。
我们通过以下示例演示装饰器模式的使用,在该示例中,我们将使用某种颜色装饰形状而不改变形状类别。
我们将创建一个Shape接口和实现Shape接口的具体类。然后,我们将创建一个抽象装饰器类ShapeDecorator,该类实现Shape接口并将Shape对象作为其实例变量。
RedShapeDecorator是实现ShapeDecorator的具体类。
DecoratorPatternDemo ,我们的演示类将使用RedShapeDecorator装饰Shape对象。
创建一个接口。
Shape.java
public interface Shape {
void draw();
}
创建实现相同接口的具体类。
Rectangle.java
public class Rectangle implements Shape {
@Override
public void draw() {
System.out.println("Shape: Rectangle");
}
}
Circle.java
public class Circle implements Shape {
@Override
public void draw() {
System.out.println("Shape: Circle");
}
}
创建实现Shape接口的抽象装饰器类。
ShapeDecorator.java
public abstract class ShapeDecorator implements Shape {
protected Shape decoratedShape;
public ShapeDecorator(Shape decoratedShape){
this.decoratedShape = decoratedShape;
}
public void draw(){
decoratedShape.draw();
}
}
创建扩展ShapeDecorator类混凝土装饰类。
RedShapeDecorator.java
public class RedShapeDecorator extends ShapeDecorator {
public RedShapeDecorator(Shape decoratedShape) {
super(decoratedShape);
}
@Override
public void draw() {
decoratedShape.draw();
setRedBorder(decoratedShape);
}
private void setRedBorder(Shape decoratedShape){
System.out.println("Border Color: Red");
}
}
使用RedShapeDecorator装饰Shape对象。
DecoratorPatternDemo.java
public class DecoratorPatternDemo {
public static void main(String[] args) {
Shape circle = new Circle();
Shape redCircle = new RedShapeDecorator(new Circle());
Shape redRectangle = new RedShapeDecorator(new Rectangle());
System.out.println("Circle with normal border");
circle.draw();
System.out.println("\nCircle of red border");
redCircle.draw();
System.out.println("\nRectangle of red border");
redRectangle.draw();
}
}
验证输出。
Circle with normal border
Shape: Circle
Circle of red border
Shape: Circle
Border Color: Red
Rectangle of red border
Shape: Rectangle
Border Color: Red