Where to add a do while loop to have the program repeat or terminate?

Question

I'm new to programming, this is my first Java class. I've gotten a code to calculate temperature from celsius to fahrenheit and vice versa, but I cannot figure out where I should have entered a Do While loop to have the program repeat or terminate.

import java.util.Scanner;

public class PracticeTemp {
    private static float f = 0, c = 0;
    private static final Scanner scan = new Scanner (System.in);
    private static int converChoice = 1;

    public static void main(String [] args) {
    System.out.println("Press 1 for C->F or 2 for F->C 3 to Quit");
    converChoice = scan.nextInt();

    if (converChoice == 1) 
        convertCtoFAndPrint();
    else if
    (converChoice == 2) 
        convertFtoCAndPrint();
    else if
    (converChoice == 3)
    System.out.println("The program will now terminate");
    System.exit(0);

    }

    public static void convertFtoCAndPrint() {
    System.out.println("Please enter degrees F");
    f = scan.nextFloat();

    c = (5* (f - 32)) / 9f;

    System.out.println(f + " degrees F is " + c + " degrees C.");
    }

     public static void convertCtoFAndPrint() {
    System.out.println("Please enter degrees C");
    c = scan.nextFloat();

    f = (9 * c + 160) / 5f;

    System.out.println(c + " degrees C is " + f + " degrees F.");
    }
}

Answer 1

In order for the program to repeat and get input from the console you have to include a

while(true){
    //this is an infinite loop
}

in the main function where the user inputs data:

public static void main(String [] args) {
        while(true) { //this in an infinite loop
            System.out.println("Press 1 for C->F or 2 for F->C 3 to Quit");
            converChoice = scan.nextInt();

            if (converChoice == 1)
                convertCtoFAndPrint();
            else if (converChoice == 2)
                convertFtoCAndPrint();
            else if (converChoice == 3) {
                System.out.println("The program will now terminate");
                System.exit(0);//this stops the program
            }
        }
    }

Or you can add:

do{

}while(converChoice!=3);

This repeats as long as convertChoice (user input) is not equal to 3

public static void main(String [] args) {
        do {
            System.out.println("Press 1 for C->F or 2 for F->C 3 to Quit");
            converChoice = scan.nextInt();

            if (converChoice == 1)
                convertCtoFAndPrint();
            else if (converChoice == 2)
                convertFtoCAndPrint();
            else if (converChoice == 3) {
                System.out.println("The program will now terminate");
                // System.exit(0); is no longer needed since the program exists the loop
            }
        } while (converChoice!=3);
    }

Answer 2

You could put it arround the code inside the main method body such that every time the first execution of the program is complete, it repeats by showing the "Press 1 ..." message, re-accepting input and so on.

public static void main(String[] argz){
   do{
      //Do stuff.
   }while(condition);
}

In your case, the condition should be something along the lines of converChoice != 3 which will essentially stop when converChoice is equal to 3.