Java scanner requiring multiple inputs

Question

I'd like to ask a question about my code.

I apologize for the inefficiency and the messiness of it, I am still trying to learn java.

    System.out.println("Please choose the number corresponding to the operation: ");
    System.out.println("1 for add,2 for subtract,3 for multiply, 4 for divide, 5 for print, and 6 for exit: ");

    if (sc.nextInt() == 5) {
        System.out.println("Your first fraction is: " + num1 + "/" + denom1 + " or in decimal: " + ((float) num1 / denom1));
        System.out.println("Your second fraction is: " + num2 + "/" + denom2 + " or in decimal: " + ((float) num2 / denom2));
    } else if (sc.nextInt() == 3) {
        System.out.println("Multiply: " + (num1 * num2) + "/" + (denom1 * denom2));

    } else if (sc.nextInt() == 4) {
        System.out.println("Divide: " + (num1 * denom2) + "/" + (denom1 * num1));

    } else if (sc.nextInt() == 1) {
        int d = denom1 * denom2;
        int n1 = num1 * denom2;
        int n2 = num2 * denom1;
        System.out.println("Addition: " + (n1 + n2) + "/" + d);


    } else if (sc.nextInt() == 2) {
        int d = denom1 * denom2;
        int n1 = num1 * denom2;
        int n2 = num2 * denom1;
        System.out.println("Subtract: " + (n1 - n2) + "/" + d);
    }
    else if (sc.nextInt() == 6 ) {
        System.exit(0);
    }
}
}

When I run the program, the first if statement gets by fine, as I only have to input the number 5 one time. However as you can see from the second else if statement which is the number 3 requires two inputs, I have to enter it two times before the next line comes up. The third else if statement which is the number 4 requires 3 inputs before the next line shows up, and so on with each successive else if statement. I'm sorry if I am not explaining this properly, Does anyone have any idea why this is happening?

Answer 1

Change your code to:

int input = sc.nextInt();
sc.nextLine();
if (input == 5) {

and all other if (sc.nextInt()...) also.

nextInt will consume your input. So if you come to the second if the input is alredy consumed by the first if .

nextLine is nessesary to consume the <ENTER> after the int value.

Answer 2

         Try to use switch statement.
    package practice;
    import java.util.Scanner;
    public class Stack{
    public static void main(String[] args) {
    Scanner sc=new Scanner(System.in);  
    System.out.println("ENTER THE 2 NUMBERS");
    int num1=sc.nextInt();
    int num2=sc.nextInt();
    System.out.println("ENTER THE CHOICE");
    int choice='0';
    while(choice!=6)
    {
         choice=sc.nextInt();
        System.out.println(choice);
    switch(choice)
    {
    case 1:
         int add=num1+num2;
        System.out.println("Addition:"+add);
        break;
    case 2:
          System.out.println("Subtract:");
        break;
    case 3:
          System.out.println("Multiply:");
        break;
    case 4:
        System.out.println("Divide:");
        break;
    case 5:
         System.out.println("Your first fraction is:");
         System.out.println("Your second fraction is:");
        break;
    case 6:
        System.exit(0);
        break;
    default:
        System.out.println("LOSER");
        break;
           }
                            }       
    sc.close();
                }
     }