这个程序在我输入无效输入后，我需要从头开始，我怎么能在java中做到这一点？

Question

System.out.println(" Enter the three sides of Triangle ");
       Scanner s = new Scanner (System.in);
       
       System.out.print(" a = "  ); 
       double a = s.nextDouble();
       
       System.out.print(" b = "  ); 
       double b = s.nextDouble();

       System.out.print(" c = "  ); 
       double c = s.nextDouble();

       if ( a+b>c && b+c>a && c+a>b && a!=0  && b!=0  && c!=0    )
       {
           
           System.out.println("The perimeter of a Triangle = " + (a+b+c));
           
       } 
       else {
           
       System.out.println(" invalid inputs  ");                                

       }

Answer 1

您可以创建一个while 循环，该循环在用户输入有效数字时中断，并继续输入直到用户继续输入无效输入，如下所示：

        System.out.println(" Enter the three sides of Triangle ");
        Scanner s = new Scanner(System.in);

        while (true) {
            System.out.print(" a = ");
            double a = s.nextDouble();

            System.out.print(" b = ");
            double b = s.nextDouble();

            System.out.print(" c = ");
            double c = s.nextDouble();

            if (a + b > c && b + c > a && c + a > b && a != 0 && b != 0 && c != 0) {
                System.out.println("The perimeter of a Triangle = " + (a + b + c));
                break; // Break on valid input
            } else {
                System.out.println(" invalid inputs  ");
            }
        }

Answer 2

由于 java 是 OOP 语言，我总是喜欢朝那个方向思考，它可以为您的问题提供以下解决方案：

class Triangle {
  double a, b, c;
  public void enterSides(Triangle t){
    //Get inputs from user into t.a, t.b and t.c
  }

  public bool checkSides(Triangle t){
    //if triangle condition is valid, return true else false
  }
}

class Solution{
  public static void main(String args[])
  {
    Triangle t=new Triangle();
    t.enterSides();
    if(t.checkSides()) {
      //print parimeter
    }
    else{
      t.enterSides();
    }
  }

}