Continuous input gathering until conditions met?

Question

I am trying to understand gathering user input and looping until conditions. I want to loop a scanner until user inputs 0, however, I need each inputted integer to be stored so it can be accessed for later use. The hard part is, I can't use an array.

Is this in Java? Also if you can't use an array...what can you use? — William Gaul, Sep 23 '13 at 22:40
Well, arrays and lists are basic data structures for storing things. I can't think of anything else where you can store for future usages. — RandomQuestion, Sep 23 '13 at 22:46
use a string and your own seperator. Troll the condition of not using arrays — Osama Javed, Sep 23 '13 at 22:47
Since you don't know the number of elements in user input, you can't use simple `Array` because to initialize arrays, you need to know the initial size. Easiest approach would be to use `ArrayList` which uses `Array` in it's backend. Refer to my answer. — RandomQuestion, Sep 23 '13 at 22:57
Use an ArrayList, Stack, Queue, or Set. See my answer below, you have many options. — ElliotSchmelliot, Sep 23 '13 at 23:00

Zeeshan · Answer 1 · 2013-09-23T22:58:03.990

0

simply you can do something like

List mylist = new ArrayList(); //in java. other wise you can create array[size]
int input = 1;
while(input!=0)
{
  /* input number from user here */

  if(input!=0)
  mylist.add(input);

}

edited Sep 23 '13 at 22:58

answered Sep 23 '13 at 22:49

Zeeshan

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ElliotSchmelliot · Answer 2 · 2013-09-23T22:58:38.227

Here is an easy way to loop user input until 0 is entered.

Scanner console = new Scanner(System.in);
boolean loop = true;
String input;
while(loop) {
    input = console.nextLine();
    //Add input to a data structure
    if (input.equals("0")) {
        loop = false;
    }
}

As far as adding the user input to a data structure, you said you can't use an Array. How about a List or a Set. Even a Stack or a Queue would work. Have you looked at using any of these data structures?

Here is a basic example using a List:

List<String> aList = new ArrayList<String>();
aList.add(input);

And this is how you might use a Stack:

Stack<String> stk = new Stack<String>();
stk.push(input);

Perhaps the most efficient way would be to use a HashSet:

Set<String> set = new HashSet<String>();
set.add(input);

score 0 · Answer 3 · edited May 23 '17 at 10:31

Using arrays here would be little tricky since you don't know the numbe of elements user is going to enter. You can always write the code to create a new array with bigger capacity once user has exhaused initial capacity and copy over existing input elements but using List would be much easier.

    Scanner scanner = new Scanner(System.in);

    List<Integer> input = new ArrayList<>();
    int nextInt = Integer.MIN_VALUE;
    while((nextInt = scanner.nextInt()) != 0){
        input.add(nextInt);
    }

See this question if you really want to use arrays. Answer explains on creating new arrays and copying over elements. Java dynamic array sizes?

Continuous input gathering until conditions met?

3 Answers3