JAVA中装饰模式的理解

以下的代码很好的反映了装饰模式的效果。

变量的相互包含关系如下图所示，所以才会产生出最后的打印结果。

package SoftTest;

public class Soft {
public static void main(String[] args) {
Invoice t = new Invoice();
Invoice tk = new HeadDecorator(new FootDecorator(t));
tk.printInvoice();
}
}


class Invoice {
public void printInvoice() {
System.out.println("this is content");
}
}


class Decorator extends Invoice {
protected Invoice ticket;


public Decorator(Invoice t) {
ticket = t;
}


public void printInvoice() {
if (ticket != null) {
ticket.printInvoice();
}
}
}


class HeadDecorator extends Decorator {
public HeadDecorator(Invoice t) {
super(t);
System.out.println("HeadDecorator create");
}


public void printInvoice() {
System.out.println("this is head");
super.printInvoice();
}
}


class FootDecorator extends Decorator {
public FootDecorator(Invoice t) {
super(t);
System.out.println("FootDecorator create");
}


public void printInvoice() {
super.printInvoice();
System.out.println("this is foot");
}

}

打印结果：

FootDecorator create
HeadDecorator create
this is head
this is content
this is foot