【JAVA】編寫一個類Calculator,有兩個屬性num1,num2,這兩個數據的值，不能在定義的同時初始化，最後實現加減乘 除四種運算.

兩種方法：

1.使用構造函數：

class Calculator{
        private int num1;
        private int num2;

      public Calculator() {

      }
      public Calculator(double num1,double num2) {
          this.num1 = num1;
          this.num2 = num2;
      }
         public double add(double num1, double num2){
            this.num1= num1;
            this.num2= num2;
            return this.num1+this.num2;
        }

      public double sub(double num1, double num2){
         this.num1=num1;
         this.num2=num2;
         return this.num1-this.num2;
     }

     public double mul(double num1, double num2){
         this.num1=num1;
         this.num2=num2;
         return this.num1*this.num2;
     }

     public double div(double num1, double num2){
         this.num1=num1;
         this.num2=num2;
         return this.num1/this.num2;
     }
  }
    
    public class Test1 {
    public static void main(String[] args) {
        Calculator calculator = new  Calculator(5.9，9.);//實例化對象
        System.out.println(calculator.add());
        System.out.println(calculator.sub());
        System.out.println(calculator.mul());
        System.out.println(calculator.div());
   }

運行結果:

class Calculator{
        private double num1;
        private double num2;
 
      public double getNum1() {
        return num1;
      }

      public void setNum1(double num1) {
          this.num1 = num1;
      }

      public double getNum2() {
          return num2;
      }

      public void setNum2(double num2) {
          this.num2 = num2;
      }
      public double add(double num1, double num2){
            this.num1= num1;
            this.num2= num2;
            return this.num1+this.num2;
        }

      public double sub(double num1, double num2){
         this.num1=num1;
         this.num2=num2;
         return this.num1-this.num2;
     }

     public double mul(double num1, double num2){
         this.num1=num1;
         this.num2=num2;
         return this.num1*this.num2;
     }

     public double div(double num1, double num2){
         this.num1=num1;
         this.num2=num2;
         return this.num1/this.num2;
     }

}
    public class Test1 {
    public static void main(String[] args) {
        Calculator calculator = new  Calculator();
      
        calculator.setNum1(10.0);
        calculator.setNum2(12.2);
        
        System.out.println(calculator.add());
        System.out.println(calculator.sub());
        System.out.println(calculator.mul());
        System.out.println(calculator.div());
  }
}

運行結果：