比较数组列表中的两个元素

Question

The exercise is, to create an arraylist for a class, where a User can enter "Guestnumber" + "Guestname" + "Guestemail".

Everything works fine expect if I create a new Guest with the Guestnumber 1 for example, the program should tell me "Guestnumber is existing, please choose a new one". I trief and came to this, not working conclusion:

public void gastAnlegen() {
    boolean pruef1 = true;
    boolean pruef2 = true;
    boolean pruef3 = true;
    boolean gastNummerPruefung = false; 
    while(gastNummerPruefung != true) {
        gastNummerPruefung = true;


    while (pruef1 != false) {
        System.out.println("Bitte Gästenummer eingeben: ");
        String gNr = input.next();
        try {
            gast = Integer.parseInt(gNr);
        } catch (NumberFormatException e) {
            continue;
        }
        pruef1 = false;
        for (Gast test : verwaltungG) {
            if (gast == test.getgNr()) {
                System.out.println("Diese Nummer ist leider schon vergeben");
                gastNummerPruefung = false;
            }
        }

        }
    }

The Problem now is that it wont go further than telling me to enter the Guestnumber ("Bitte Gästenummer eingeben") over and over again, so it kinda stops there.

I added The "bigger" while loop to test if the number is existing.

Where is the error?

Gast ist the Class for get, set

gastNmmerPruefung boolean for the loop

before i added the big loop, it worked fine.

Edit: Okay i found one problem, I had to change "gastNmmerPruefung to true after the big while, but it still doesnt let me enter a new number after it says that the number already exists.

Answer 1

You also need to change your pruef1 back to true if you find that the number is already taken to make it go inside the inner while loop:

    for (Gast test : verwaltungG) {
        if (gast == test.getgNr()) {
            System.out.println("Diese Nummer ist leider schon vergeben");
            gastNummerPruefung = false;
            pruef1 = true;
        }
    }

Answer 2

You really only need one boolean to check. Get the number from the user, check it, if it's found then ask again, otherwise your done.

Try this:

while(!gastNummerPruefung)
{
    System.out.println("Bitte Gästenummer eingeben: ");
    String gNr = input.next();
    try
    {
        gast = Integer.parseInt(gNr);
    }
    catch (NumberFormatException e)
    {
        continue;
    }

    for (Gast test : verwaltungG)
    {
        if (gast == test.getgNr())
        {
            System.out.println("Diese Nummer ist leider schon vergeben");
            gastNummerPruefung = false;
        }
        else
            gastNummerPruefung = true;
    }
}

Answer 3

You should check first inner loop.. Try this. You have to faced problem with second inner loop

while(gastNummerPruefung != true) 
gastNummerPruefung = false;
while (pruef1 != false) {
    System.out.println("Bitte Gästenummer eingeben: ");
    String gNr = input.next();
    try {
        gast = Integer.parseInt(gNr);
    } catch (NumberFormatException e) {
        continue;
    }
    pruef1 = true;  // change this in your code
    for (Gast test : verwaltungG) {
        if (gast == test.getgNr()) {
            System.out.println("Diese Nummer ist leider schon vergeben");
            gastNummerPruefung = false;
        }
    }

    }