android - stack=java.lang.StackOverflowError: stack size 8MB -

i'm getting stackoverflow error, understand fully, issue im not dealing big data, how can error produced ?

i have activity, framelayout, fragment, 3 options.

in fragment, when click on 1 of options, re-create fragment , put random numbers, max 15, not big, error happens when user click fast on options cause overflow.

this code generating, ideas "enhancing" ? don't know if code bad practice momery using.

private static list<integer> savednumbers;  public static void setupsavednumberslist(){     savednumbers = new arraylist<>(); }   static list<integer> range; private static void adddiff(int mmax){     range = new arraylist<>();     for(int = 0 ; < mmax ; i++){         range.add(i);     }      range.removeall(savednumbers); }  private static int returnifduplic(int mmax){     adddiff(mmax);     return new random().nextint(range.size()); }   public static int returnuniquesavednumber(int mmax){     int random = returnrandom(mmax);     if(savednumbers != null && savednumbers.size() > 0) {         if(doessavednumberexist(random)){             return returnifduplic(mmax);         } else {             savednumbers.add(random);             return random;         }     } else if (savednumbers != null && savednumbers.size() == 0){         savednumbers.add(random);         return random;     } else if( savednumbers == null){         setupsavednumberslist();         return returnuniquesavednumber(mmax);     } else {         return 1;     } }  private static boolean doessavednumberexist(int number){     for(int s: savednumbers){         if(number == s)             return true;     }     return false; }  private static int returnrandom(int mmax){     return new random().nextint(mmax); } 

this line recursing if happen random same number have saved:

if(doessavednumberexist(random)){     return returnuniquesavednumber(mmax); }  

if have saved 1-15, , max 15 guarantee stack-overflow never satisfy if statement. bad approach of "random number no good, try again", since add more , more numbers add more , more recursions. better approach may have random number used index possible numbers left choose.