while loop - Java recursion class variable value is reset to 0 -

i trying implement coin change problem using recursion. have written following code , facing problem static class variable. 'answer' class variable , trying add return value in loop. works fine within while loop after while loop ends answer reset 0;

    while (i * currentcoin <= sum) {     system.out.println("inside while; answer " + answer);           answer = answer             + findcombinations(                     sum - * currentcoin,                     new arraylist<integer>(denominations.sublist(1,                             denominations.size())));     i++;  } 

below code have written. can copy , run check.

    import java.util.arraylist;     import java.util.collections;      public class coinchangehashmap { static int answer = 0;  public static void main(string[] args) {      int[] array = new int[] { 7, 3, 2 };     arraylist<integer> input = new arraylist<integer>();     getlist(array, input);     findcombinations(12, input);     system.out.println(answer); }  private static void getlist(int[] array, arraylist<integer> input) {      (int : array) {         input.add(i);     }  }  public static int findcombinations(int sum, arraylist<integer> denominations) {      if (denominations.size() == 1) {         if (sum % denominations.get(0) == 0) {             return 1;         }         return 0;      }     int = 0;     int currentcoin = denominations.get(0);      while (i * currentcoin <= sum) {         system.out.println("inside while; answer " + answer);          answer = answer                 + findcombinations(                         sum - * currentcoin,                         new arraylist<integer>(denominations.sublist(1,                                 denominations.size())));         i++;      }     return 0; }} 

**the output 0. expected output 4. while debugging output got **

inside while; answer 0 inside while; answer 0 inside while; answer 1 inside while; answer 1 inside while; answer 2 inside while; answer 2 inside while; answer 0 inside while; answer 0 inside while; answer 0 0 

any appreciated.

the problem related odd code structure, in convey outcome of recursive call modifying static variable answer, , via method's return value.

if analyzed problem more closely, discover not upon exit loop partial results lost, rather time after return method. therefore, consider way update answer:

answer = answer + findcombinations( /* ... */ ); 

at top-most level of recursion, answer 0. when java evaluates above expression, evaluates first left operand , right operand, adds them. is, evaluates answer, getting result 0, before performs recursive call. value of answer may updated in course of recursive call, changes come late. bottom-most level of recursion ever returns value different zero, if recursive call recurses @ least 1 level deeper return zero. in case, sum computed 0 + 0, , assigned answer, clobbering update method performed.

you resolve problem swapping order of operands in sum, better, , not harder, rid of static variable altogether. use local variable within method accumulate results, , in cases convey total caller via method's return value.