Java学习笔记——设计模式之一.简单工厂

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类图：

定义Operation类

 package cn.no1.simplefactory;

 public abstract class Operation {

     private double numA;
     private double numB;

     public double getNumA() {
         return numA;
     }

     public void setNumA(double numA) {
         this.numA = numA;
     }

     public double getNumB() {
         return numB;
     }

     public void setNumB(double numB) {
         this.numB = numB;
     }

     public abstract double calculate ();
 }

定义其四个子类

 package cn.no1.simplefactory;

 public class OperationAdd extends Operation{

     @Override
     public double calculate() {
         // TODO Auto-generated method stub
         return this.getNumA() + this.getNumB();
     }

 }
 public class OperationSub extends Operation {

     @Override
     public double calculate() {
         // TODO Auto-generated method stub
         return this.getNumA()-this.getNumB();
     }

 }
 public class OperationMultiply extends Operation{

     @Override
     public double calculate() {
         // TODO Auto-generated method stub
         return this.getNumA()*this.getNumB();
     }

 }
 public class OperationDivide extends Operation{

     @Override
     public double calculate() {
         // TODO Auto-generated method stub
         return this.getNumA()/this.getNumB();
     }

 }

定义工厂类

 package cn.no1.simplefactory;

 public class OperationFactory {

     public static Operation createOperation(String operator){
         Operation operation = null;
         switch (operator) {
         case "+":
             operation = new OperationAdd();
             break;
         case "-":
             operation = new OperationSub();
             break;
         case "*":
             operation = new OperationMultiply();
             break;
         case "/":
             operation = new OperationDivide();
             break;
 　　　　 }
         return operation;
     }
 }

测试类:

 package cn.no1.simplefactory;

 import java.util.Scanner;

 public class _Test {

     public static void main(String[] args) {
         Scanner sc = new Scanner(System.in);
         System.out.println("输入数字1:");
         double numA = sc.nextDouble();
         System.out.println("输入数字2:");
         double numB = sc.nextDouble();
         System.out.println("输入操作符:");
         String operator = sc.next();
         sc.close();
         Operation operation = OperationFactory.createOperation(operator);
         operation.setNumA(numA);
         operation.setNumB(numB);
         double result = operation.calculate();
         System.out.println("计算结果是:"+result);
     }
 }