大话设计模式之简单工厂模式

背景需求:

模拟一个简单计算器。

UML类图:

说明:

抽象类AbstractOperation有一个抽象方法getResult和两个成员变量,加减乘除分别继承AbstractOperation并实现getResult方法即可。OperationFactory是一个简单工厂方法,可根据入参实例化不同的子类。

demo:

AbstractOperation类:

 1 public abstract class AbstractOperation {
 2 
 3     private Double firstNumber;
 4     private Double secondNumber;
 5 
 6     public abstract Double getResult() throws Exception;
 7 
 8     public Double getFirstNumber() {
 9         return firstNumber;
10     }
11 
12     public void setFirstNumber(Double firstNumber) {
13         this.firstNumber = firstNumber;
14     }
15 
16     public Double getSecondNumber() {
17         return secondNumber;
18     }
19 
20     public void setSecondNumber(Double secondNumber) {
21         this.secondNumber = secondNumber;
22     }
23 }

加法类OperationAdd:

1 public class OperationAdd extends AbstractOperation {
2     @Override
3     public Double getResult() {
4         return getFirstNumber() + getSecondNumber();
5     }
6 }

减法类OperationSub:

1 public class OperationSub extends AbstractOperation {
2     @Override
3     public Double getResult() {
4         return getFirstNumber() - getSecondNumber();
5     }
6 }

简单工厂类OperationFactory:

 1 public class OperationFactory {
 2 
 3     public static AbstractOperation createOperation(String operate){
 4         AbstractOperation operation = null;
 5 
 6         switch (operate){
 7             case "+":operation = new OperationAdd();break;
 8             case "-":operation = new OperationSub();break;
 9             default:break;
10         }
11         return operation;
12     }
13 }

客户端测试类:

 1 public class Main {
 2 
 3     public static void main(String[] args) throws Exception {
 4 
 5         AbstractOperation operation = 
 6    OperationFactory.createOperation("+");
 7         operation.setFirstNumber(10d);
 8         operation.setSecondNumber(20d);
 9         System.out.println(operation.getResult());
10 
11     }
12 }

总结:

简单工厂模式适用于需要创建大量相同类型(父类相同或实现相同接口)实例的情景

posted @ 2018-05-06 20:22  浅夏丶未央  阅读(128)  评论(0编辑  收藏