Java Scanner Array

Question

I am having troubles with java. I need to scan numbers (example: 1 3 4 2 5 6 7) and put them into array. The problem is I don't know how long it will be. Is there a command that I can use to determine the length of the numbers putted in scanner?

Answer 1

If you don't want to use ArrayList, as a workaround, I advice to read the entire line and then split to get the length and individual values:

   String line = scanner.nextLine();
   String[] values = line.split(" ");
   int[] intValues = new int[values.length];
   int indx = 0;
   for(String value:values){
     intValues[indx++] = Integer.parseInt(value);
   }

EDIT: Second approach:

   List<Integer> numList = new ArrayList<Integer>();
   int number = 0;
   while (number != -1) {
      System.out.println("Enter a positive integer value (or -1 to stop): ");
      number = Integer.parseInt(in.nextLine());
      if (number != -1){
        numList.add(number);
      }
   }
   in.close();

   Integer[] numArray = numList.toArray(new Integer[numList.size()]);

EDIT2: Taking care of multiple numbers in the same line and terminating at empty line

List<Integer> numList = new ArrayList<Integer>();
while(true) {
   System.out.println("Enter a positive integer value (or -1 to stop): ");
   String line = in.nextLine();
   if(line.length() <1){
      break;
   }
   String [] numbers = line.split(" ");
   for(String num: numbers){
          numList.add(Integer.parseInt(num));
   }
 }
 in.close();

 Integer[] numArray = numList.toArray(new Integer[numList.size()]);

Answer 2

Use an ArrayList if you want a variable-size collection.

ArrayList<Integer> lst = new ArrayList<Integer>();
lst.add(scanner.getInt());

Answer 3

You can use an ArrayList. Just fill it up and at the end, convert it to an integer array. Or even better, keep the list and work with that.

Scanner in = new Scanner(System.in);

ArrayList<Integer> intList = new ArrayList<Integer>();
while (true) {
  System.out.println("Enter a positive integer value (or -1 to stop): ");
  int number = in.nextInt();
  if (number < 0) break;
  intList.add(number);
}
// just use this last line if you really want an array. Work with the list instead if possible.
Integer[] yourFinalArray = intList.toArray(new Integer[0]);

Answer 4

If you use the google Guava library ( https://code.google.com/p/guava-libraries/ ) you can say:

String numbers="1 3 4 2 5 6 7";
Splitter.on(" ").split( numbers );

this gives you an iterable. If you insist on getting an array of Strings, you can say:

Iterables.toArray(Splitter.on(" ").split( numbers ), String.class)