1业务和逻辑写在一起

import java.util.*;
import java.io.Console;
class Factory
{
    public static void main(String[] args) 
    {
        try
        { 
            System.out.println("工厂模式");
            Console console = System.console();
            String strNumberA = console.readLine("请输入数字A:");
            String strOperate = console.readLine("请输入运算符号(+-*/):");
            String strNumberB = console.readLine("请输入数字B:");
            String strResult = "";
            switch (strOperate)
               {
                case "+":
                    strResult = String.valueOf(Double.valueOf(strNumberA) + Double.valueOf(strNumberB));
                    break;
                case "-":
                    strResult = String.valueOf(Double.valueOf(strNumberA) - Double.valueOf(strNumberB));
                    break;
                case "*":
                    strResult = String.valueOf(Double.valueOf(strNumberA) * Double.valueOf(strNumberB));
                    break;
                 case "/":
                     if (strNumberB != "0")
                         strResult = strResult = String.valueOf(Double.valueOf(strNumberA) / Double.valueOf(strNumberB));
                     else
                         strResult = "除数不能为0";
                    break;
            
            }
            System.out.println("结果是: " + strResult);
        }
        catch (Exception ex) 
        {
            System.out.println("错了");
        } 

    }
}

2运算和显示分开

import java.util.*;
import java.io.Console;
class Decouping {
    public static class Operation {
            public static double GetResult(double numberA, double numberB, String operate) {
            double result = 0d;
            switch (operate) {
                case "+":
                    result = numberA + numberB;
                    break;
                case "-":
                    result = numberA - numberB;
                    break;
                case "*":
                    result = numberA * numberB;
                    break;
                case "/":
                    if (numberB != 0)
                        result = numberA / numberB;
                     else
                        result = 0;
                    break;
            } 
            return result;
        }
    }
    public static void main(String[] args) {
        try {
            System.out.println("工厂模式");
            Console console = System.console();
            String strNumberA = console.readLine("请输入数字A:");
            String strOperate = console.readLine("请输入运算符号(+-*/):");
            String strNumberB = console.readLine("请输入数字B:");
            String strResult = "";
            strResult = String.valueOf(Operation.GetResult(Double.valueOf(strNumberA), Double.valueOf(strNumberB), strOperate));
            System.out.println("结果是: " + strResult);
        }
       catch (Exception ex) {
           System.out.println("您的输入有错");
       }
    }
}

3简单工厂

import java.util.*;
class Operation {
    double numberA = 0;
    double numberB = 0;
    private double result = 0;
    public void setNumberA(double numberA){
        this.numberA = numberA;
    }
    public double getNumberA(double numberA){
        return numberA;
    }
    public void setNumberB(double numberB){
        this.numberB = numberB;
    }
    public double getNumberB(double numberB){
        return numberB;
    }
    public double GetResult() {
        double result = 0;
        return result;
    }
}
class OperationAdd extends Operation {
    public double GetResult() {
        double result = 0;
        result = numberA + numberB;
        return result;
    }
}
class OperationSub extends Operation {
    public double GetResult() {
        double result = 0;
        result = numberA - numberB;
        return result;
    }
}
class OperationMul extends Operation {
    public double GetResult() {
        double result = 0;
        result = numberA * numberB;
        return result;
    }
}
class OperationDiv extends Operation {
    public double GetResult() {
        double result = 0;
        // if ( numberB == 0 )
            // throw new Exception("除数不能为0");
        result = numberA / numberB;
        return result;
    }
}
class LXJSimpleFactory {
    public static Operation createOperate(String operate) {
        Operation oper = null;
        switch (operate) {
            case "+":      
                oper = new OperationAdd();
                break;
            case "-":
                oper = new OperationAdd();
                break;
            case "*":
                oper = new OperationAdd();
                break;
            case "/":
                oper = new OperationAdd();
                break;
        }
        return oper;
    }
}
public class SimpleFactory {
    public static void main(String[] args) {
       System.out.println("简单工厂");
       Operation oper;
       oper = LXJSimpleFactory.createOperate("+");
       oper.numberA  = 1;
       oper.numberB  = 29;
       double result = oper.GetResult();
       System.out.println("1+29 is:" + result); 
   }
}

简单工厂.png