【设计模式】简单工厂模式

//两个数字运算
public static void main(String[] args) {
      double number1=10;
      double number2=3;
      String optSign="*";
      double cal = CalFactory.cal(number1, number2,optSign);
      System.out.println(cal);
  }

public class CalFactory {

    public static double cal(double num1,double num2,String optSign) {

        CalModel calModel;
        switch (optSign){
            case "+":
                calModel=new CalModelAdd();
                break;
            case "-":
                calModel=new CalModelSub();
                break;
            case "*":
                calModel=new CalModelMul();
                break;
            case "/":
                calModel=new CalModelDiv();
                break;
            default:
                throw new IllegalStateException("Unexpected value: " + optSign);
        }
        return calModel.cal(num1, num2);
    }
}

public class CalModel {
    public double cal(double number1,double number2){
        return 0;
    }
}

加法

public class CalModelAdd extends CalModel {

    @Override
    public double cal(double number1, double number2) {
        return NumberUtil.add(BigDecimal.valueOf(number1)).add(BigDecimal.valueOf(number2)).doubleValue();
    }
}

减法

public class CalModelSub extends CalModel {

    @Override
    public double cal(double number1, double number2) {
        return NumberUtil.add(BigDecimal.valueOf(number1)).subtract(BigDecimal.valueOf(number2)).doubleValue();
    }
}

乘

public class CalModelMul extends CalModel {

    @Override
    public double cal(double number1, double number2) {
        return NumberUtil.add(BigDecimal.valueOf(number1)).multiply(BigDecimal.valueOf(number2)).doubleValue();
    }
}

除法

public class CalModelDiv extends CalModel {

    @Override
    public double cal(double number1, double number2) {
        return NumberUtil.add(BigDecimal.valueOf(number1)).divide(BigDecimal.valueOf(number2), RoundingMode.HALF_UP).doubleValue();
    }
}