呆呆的計(jì)算器(version 1.0)
這段代碼是來(lái)自大話，小菜最開始的面試代碼。小菜是一個(gè)小白轩娶。嗯，小菜果然是個(gè)小白框往。小菜好白鳄抒。

public class Program {
    public static void main(String[] args) {
        int result = 0;
        System.out.println("請(qǐng)輸入數(shù)字A");
        String a = "123";
        System.out.println("請(qǐng)選擇運(yùn)算符號(hào)（+、-椰弊、*许溅、/）：");
        String b = "+";
        System.out.println("請(qǐng)輸入數(shù)字B");
        String c = "321";
        String d = "";

        if (b.equals("+"))
            result = Integer.parseInt(a) + Integer.parseInt(c);
        c = result + "";
        System.out.println(c);
    }
}

呆呆計(jì)算器(version 2.0)
老鳥說(shuō)小菜，寫的代碼不規(guī)范秉版。不是一個(gè)合格的牛馬贤重。然后小菜勵(lì)志要做一個(gè)合格的牛馬，然后改了一版清焕。
規(guī)范了命名并蝗。

public class Program2 {
    public static void main(String[] args) {
        System.out.println("請(qǐng)輸入數(shù)字A");
        String strNumberA = "123";

        System.out.println("請(qǐng)選擇運(yùn)算符號(hào)（+、-秸妥、*滚停、/）：");
        String strOperate = "+";

        System.out.println("請(qǐng)輸入數(shù)字B");
        String strNumberB = "321";

        String strResult = "";
        int result = 0;

        switch (strOperate) {
            case "+" :
                result = Integer.parseInt(strNumberA) + Integer.parseInt(strNumberB);
                break;
            case "-" :
                result = Integer.parseInt(strNumberA) - Integer.parseInt(strNumberB);
                break;
            case "*" :
                result = Integer.parseInt(strNumberA) * Integer.parseInt(strNumberB);
                break;
            case "/" :
                if (!strNumberB.equals("0"))
                    result = Integer.parseInt(strNumberA) / Integer.parseInt(strNumberB);
                else
                    strResult = "除數(shù)不能為0";
                break;
        }

        System.out.print("結(jié)果是 ：" + result);
        System.out.println(strResult);
    }
}

呆呆計(jì)算器(version 3.0)
把邏輯計(jì)算代碼與用戶界面代買分離

public class Operation {
    public static double getResult(double numberA, double numberB, String operate) {
        double result = 0;

        switch (operate) {
            case "+" : result = numberA + numberB;
            break;
            case "-" : result = numberA - numberB;
            break;
            case "*" : result = numberA * numberB;
            break;
            case "/" : result = numberA / numberB;
            break;
        }

        return result;
    }
}

public class Program3 {

    public static void main(String[] args) {

        System.out.println("請(qǐng)輸入數(shù)字A");
        String strNumberA = "123";

        System.out.println("請(qǐng)選擇運(yùn)算符號(hào)（+、-粥惧、*键畴、/）：");
        String strOperate = "+";

        System.out.println("請(qǐng)輸入數(shù)字B");
        String strNumberB = "321";

        String strResult = "";

        strResult =
        "" + (Operation.getResult(Double.parseDouble(strNumberA), Double.parseDouble(strNumberB), strOperate));

        System.out.print("結(jié)果是 ：" + strResult);
        System.out.println(strResult);
    }
}

呆呆計(jì)算器(version 4.0) 大招來(lái)了

基類將不變的東西放在基類，將變化的東西放在子類突雪。

public abstract class Operation2 {
    public double numberA = 0;
    public double numberB = 0;

    public double result = 0;

    public double getNumberA() {
        return numberA;
    }

    public void setNumberA(double numberA) {
        this.numberA = numberA;
    }

    public double getNumberB() {
        return numberB;
    }

    public void setNumberB(double numberB) {
        this.numberB = numberB;
    }

    public abstract double getResult_();
}

加法計(jì)算子類

public class OperationAdd extends Operation2 {
    @Override
    public double getResult_() {
        result = numberA + numberB;
        return result;
    }
}

減法計(jì)算子類

public class OperationSub extends Operation2 {
    @Override
    public double getResult_() {
        result = numberA - numberB;
        return result;
    }
}

乘法計(jì)算子類

public class OperationMul extends Operation2 {
    @Override
    public double getResult_() {
        result = numberA * numberB;
        return result;
    }
}

除法計(jì)算子類

public class OperationDiv extends Operation2 {
    @Override
    public double getResult_() {
        if (numberB != 0)
            result = numberA / numberB;
        else
//            throw new Exception("除數(shù)不能為0");
        System.out.println("除數(shù)不能為0");
        return result;
    }
}

工廠類 工廠類 工廠糞

public class OperationFactory {

    public static Operation2 operation = null;

    public static Operation2 createOperation(String opera) {
          switch (opera) {
              case "+" : operation = new OperationAdd();
              break;
              case "-" : operation = new OperationSub();
              break;
              case "*" : operation = new OperationMul();
              break;
              case "/" : operation = new OperationDiv();
              break;
          }
            return operation;
    }

Please see the magic

public class Program4 {
    public static void main(String[] args) {
        Operation2 operation = null;

        operation = OperationFactory.createOperation("+");

        operation.setNumberA(123);
        operation.setNumberB(321);

        System.out.println("" + operation.getResult_());
    }
}

真他么簡(jiǎn)潔起惕，這就是藝術(shù)！This is art.

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