Non repeating random number array

Question

I need to make a typical integer filled array with 10 random non repeating numbers from 0 to 20. Also, I need to be able to modify this so I can exclude some random numbers

Answer 1

This Method will work for you. It generate 10 unique random numbers from 0 to 20.

public static int[] getRandomArray(){
   int randomCount =10;
   int maxRandomNumber = 21;
   if(randomCount >maxRandomNumber ){
         /* if randomCount is greater than maxRandomNumber
          * it will not be possible to generate randomCount 
          * unique numbers 
          **/
          return null;
    }
    HashMap duplicateChecker = new HashMap();
    int[] arr = new int[randomCount ];
    int i = 0;
    while(i

* Edited: To make the method deterministic. And Avoid the chance of infinite loop

public static int[] getRandomArray(){
    int randomCount =10;
    int maxRandomNumber = 21;
    if(randomCount >maxRandomNumber ){
        /* if randomCount is greater than maxRandomNumber
         * it will not be possible to generate randomCount 
         * unique numbers 
         **/
        return null;
    }
    ArrayList arrayList = new ArrayList();
    // Generate an arrayList of all Integers
    for(int i=0;i