大话设计模式——简单工厂模式

书中笔记：1。代码规范性问题。2。复用性需提高。 3。封装代码，解耦合。

OperationFactory.java

package com.chenny.test;

/**
 * 简单工厂方法(Simple Factory)
 * 简单运算工厂类
 */
public class OperationFactory {
     

    public static Operation createOperate(String operate) {
     
        Operation operation = null;
        switch (operate) {
     
            case "+":
                operation = new OperationAdd();
                break;
            case "-":
                operation = new OperationSub();
                break;
            case "*":
                operation = new OperationMul();
                break;
            case "/":
                operation = new OperationDiv();
                break;
            default:
                throw new RuntimeException("不支持运算!");
        }
        return operation;
    }
}

Operation.java

package com.chenny.test;

/**
 * 简单工厂方法(Simple Factory)
 * Operation运算类
 * @author 73981
 */
public abstract class Operation {
     

    public double numberA = 0;
    public double numberB = 0;

    public abstract double getResult();

}

/**
 * 加法类
 */
class OperationAdd extends Operation {
     

    @Override
    public double getResult() {
     
        return numberA + numberB;
    }

}

/**
 * 减法类
 */
class OperationSub extends Operation {
     

    @Override
    public double getResult() {
     
        return numberA - numberB;
    }

}

/**
 * 乘法类
 */
class OperationMul extends Operation {
     

    @Override
    public double getResult() {
     
        return numberA * numberB;
    }

}

/**
 * 除法类
 */
class OperationDiv extends Operation {
     

    @Override
    public double getResult() {
     
        if (numberB == 0) {
     
            throw new RuntimeException("除数不能为0!");
        }
        return numberA / numberB;
    }

}

Calculator.java

package com.chenny.test;

import java.util.Scanner;

/**
 * 简单工厂方法(Simple Factory)
 * 客户端main方法
 */
public class Calculator {
     

    public static void main(String[] args) {
     
        Operation operation = null;
        Scanner sc = null;
        try {
     
            sc = new Scanner(System.in);
            System.out.println("请选择要进行运算的样式（+、-、*、/）");
            String symbol = sc.next();
            operation = OperationFactory.createOperate(symbol);

            System.out.println("请输入数字A");
            operation.numberA = sc.nextDouble();

            System.out.println("请输入数字B");
            operation.numberB = sc.nextDouble();

            double result = operation.getResult();
            System.out.println("计算结果为：" + result);

        }catch (Exception e){
     
            System.out.println("你输入的有误。");
        }finally {
     
            sc.close();
        }
    }

    //书中代码
//    public static void main(String[] args) {
     
//        Operation operation;
//        operation = OperationFactory.createOperate("+");
//        operation.numberA = 20;
//        operation.numberB = 10;
//        double result = operation.getResult();
//        System.out.println(result);
//    }

}