java while loop not breaking out

Question

So I am writing a program where somebody draws cards from a deck. So I wrote a while loop that loops through and checks to see if there are over 4 of the randomly created card drawn, and if there is, change the card.

here is my code:

String card = (int)Math.ceil(Math.random() * 13) + " ";
String[] used2 = used.split(" ");
//used is a String like "12 3 7 8 4 ... # etc" such that it is all the previously drawn cards.
boolean checking = true;
boolean isIn = false;
int in = 0;
int check = 0;
while(checking){
    for(int q = 0; q < used2.length; q++){
        check += 1;
        if(card.equals(used2[q] + " ")){
            in += 1;
            if(in == 4){
                System.out.println(check); //debugging line
                check += 1;
                card = (int)Math.ceil(Math.random() * 13) + " ";
                card_val = (int)Math.ceil(Math.random() * 13);
                isIn = true;
                in = 0;
                break;
            }
        }
    }
    if(isIn){
        //will execute if there is 4 of the cards already drawn so the while loop continues with a different card
        checking = true;
    }
    else{
        //breaks out of while loop because the card can be drawn
        checking = false;
    }
}
used += card;

Now this runs, but when I put it inside a for loop and set it to run like 40 times, about 2/3 times it creates an of infinite loop.

I discovered that the infinite loop is only created if the if(in == 4) statement comes out to be true.

Why is this? I have been debugging since last night and I cannot figure this out.

A cleaner way of writing your if-else statement: checking = isIn; — Bucket
– Bucket, Commented Sep 23, 2013 at 20:23
Because you set isIn to true in that block, which means checking will never get set to false. — GriffeyDog
– GriffeyDog, Commented Sep 23, 2013 at 20:24
Also a comment to (int)Math.ceil(Math.random() * 13) + " ". I suspect your reason for " " is to convert the int to String, however you can only do +"" which makes the code simpler afterwards.. — Kuba Spatny
– Kuba Spatny, Commented Sep 23, 2013 at 20:27

rgettman · Accepted Answer · 2013-09-23 20:23:44Z

6

Once you set isIn to true, you never set it back to false. So, the if statement at the bottom will keep setting checking to true, resulting in an infinite loop.

Set isIn to false at the beginning of the while loop.

while(checking){
    isIn = false;  // Add this line.
    for(int q = 0; q < used2.length; q++){

answered Sep 23, 2013 at 20:23

rgettman

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Comments

WeaponsGrade · Accepted Answer · 2013-09-23 20:39:48Z

0

Seems like a complex algorithm for a simple task.

Why not change the implementation to use simple subtraction? Initially allocate a List of all 52 values, then as you "draw" cards out of the deck, remove it from the list.

Then you can use Math.random() * list.size() to get an appropriately-ranged index?

edited Sep 23, 2013 at 20:39

answered Sep 23, 2013 at 20:27

WeaponsGrade

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1 Comment

Ryan Saxe Over a year ago

I haven't learned lists yet, this is a hw problem, we haven't even learned arrays, I've just known the split method so I used it to make manipulating the string easier

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