boolean in Java program

Hi there i'm just beginner to JAVA so 1: I got confused by how both of these variables:

    boolean firstNumberEntered=false;
    boolean secondNumberEntered=false;

control the conditions inside and outside the loop?!!.

2: what will the values before and after it exits While loop?!!

3: can the values of these variables

double firstNumber=0.0,secondNumber=0.0; 

be stored inside the boolean variables and when if it's so?!!

4: What is the relation between

boolean firstNumberEntered=false;
boolean secondNumberEntered=false;

and if-statements inside the loop!!?

Thank you:)

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);

    System.out.println("Welcome to calculations in order");

    int itemMenu=0;

    boolean userWantsToContinue=true;

    boolean firstNumberEntered=false;
    boolean secondNumberEntered=false;

    double firstNumber=0.0,secondNumber=0.0;

    while (userWantsToContinue){


        if (firstNumberEntered) {
            System.out.println("1.First number "+"(Currently): "+'('+firstNumber+')');//
        } else {
            System.out.println("1.First number "); //it will be displayed at first because its value true
        }

        if (secondNumberEntered){
            System.out.println("2.Second number "+"(Currently): "+'('+secondNumber+')');
        }else{
            System.out.println("2.Second number ");

            System.out.println("3.Takes Square");
            System.out.println("4.Takes Cube");
            System.out.println("5.Multiplication");
            System.out.println("0.Exit");

            System.out.println("\nPlease choose an item");
        switch (itemMenu=in.nextInt()){

            case 1:
                System.out.println("Please Enter First Number: ");
                firstNumber=in.nextDouble();

                firstNumberEntered=true;
                break;

            case 2:
                System.out.println("Please Enter second Number");
                secondNumber=in.nextDouble();
                secondNumberEntered=true;
                break;
            case 3:
                if(firstNumberEntered&&secondNumberEntered){
                    double square=firstNumber*secondNumber;
                    System.out.println("Square results = "+square);
                }else{
                    System.out.println("Please go back to item 1 & 2");
                }
                break;
            case 4:

                if(firstNumberEntered){
                    double cube=firstNumber*firstNumber*firstNumber;

                    System.out.println("Cube results= "+ cube);

                }else{
                    System.out.println("Please go back to 1&2");

                }


                break;
            case 5:
                if(firstNumberEntered&&secondNumberEntered){
                    double multiplication= firstNumber*secondNumber;
                    System.out.println("Multiplication of one and second number = "+multiplication);
                }else{
                    System.out.println("Please go back to item 1 & 2");
                }
                break;
            case 0:
                System.out.println("thank you visit us again لاتنسى!!");
                userWantsToContinue=false;
                break;
            default:
                System.out.println("Invalid option!!@_@");
                System.out.println("Please enter the number of the menu item you want and don't do this mistake again!!.");
                itemMenu=in.nextInt();

        }
    }
}