java - 如何结束 if 并移至另一行

Question

当我想查看条件然后移动到另一行但java中没有“goto”时，我的问题就开始了，所以我不知道如何从这个if内部移动并转到下一行当我在后面输入 return 时，它不会运行代码......如果你们能帮助我解决这个问题，我将不胜感激......源代码在这里:::

  //package CaloriesCalculator
 import java.util.Scanner;

class Main {
// @SuppressWarnings("null")
@SuppressWarnings("resource")
public static void main(String[] args) {
    // Initiate a new Scanner
    // here I have tried to use scanner
    boolean run = true;
    while(run){
    @SuppressWarnings("resource")
    Scanner userInputScanner = new Scanner(System.in);


    System.out.print("\nIf you are Male Press 1, If you are Female Press 2 ");

            int G = userInputScanner.nextInt();

            if(G == 1)

                {
                            System.out.print("Please Enter your Weight.."); 
                            int W = userInputScanner.nextInt();

                            if((W <300) && (W > 1)) {//error message


                                //      my problems start here !! I need to have the next input here but it doesn't work



                            }
                            System.out.print("Please Enter your Weight.."); 
                            W= userInputScanner.nextInt();
                            return;
                            //  int m;
                            System.out.print("Please Enter your Height");
                            int H = userInputScanner.nextInt();
                                System.out.print("Please Enter your Age.."); 
                                int A = userInputScanner.nextInt();

                                double BMR = 10*W + 6.25*H - 5*A +5 ;

                                    if( BMR > 0)    {System.out.print(" Your body needs the amount of calories : "+ BMR );}

                                        else { System.out.print("Do you know you are a mess ?  " );}





                            //int H = userInputScanner.nextInt();



                            //  else {System.out.print("Please Enter valid weight");}   
                }

            else if(G == 2)

                {

                        System.out.print("Please Enter your Weight.."); 
                        int W = userInputScanner.nextInt();

                        System.out.print("Please Enter your Height"); 
                        int H = userInputScanner.nextInt();

                        System.out.print("Please Enter your Age.."); 
                        int A = userInputScanner.nextInt();

                        double BMR = 10*W + 6.25*H - 5*A -161 ;


                                if(BMR > 0)
                                    {
                                        System.out.print(" Your body needs the amount of calories : "+ BMR );
                                    }

                                else
                                    {
                                        System.out.print("Do you know you are a mess ?  " );

                                    }


        }
            else
            {
                System.out.print(" Please put the right number or don't use program " );
            }
    }

}

}

Answer 1

nextInt()方法doesn't read the whole line (with carriage return and line feed) ，因此，当您重新读取 nextInt() 时，您会得到一个空字符串，这就是您的 if 不执行其中代码的原因。

你必须:

1. 首先使用nextLine()读取整行。

2. 使用Integer.parseInt()方法验证整数输入。

换句话说:

Scanner userInputScanner = new Scanner(System.in);
String s = userInputScanner.nextLine();

try{
    Integer.parseInt(s);
}
catch(NumberFormatException ex){
    System.out.println("Its not a valid Integer");
}

否则，您可以执行 nextInt()，然后执行 nextLine() 来使用 \n:

int number = input.nextInt();
input.nextLine(); // This line you have to add (It consumes the \n character)