java - How to set my ArrayList<integer> equal to a function? -

hello doing merge sort , think correct having hard time last 2 lines of merge_sort function... on second last line says "integer cannot resolved variable, arraylist cannot resolved variable, type mismatch: cannot convert arraylist int[]." , last line says: "type mismatch cannot convert int[] arraylist." how can fix this? appreciated!!

public static arraylist<integer>  merge_sort(arraylist<integer> b) {     if (b.size() <= 1)         system.out.println(b);       int midpoint = b.size()/2;     arraylist<integer> left = new arraylist<integer>(midpoint);     arraylist<integer> right;     if(b.size() % 2 == 0)         right = new arraylist<integer>(midpoint);     else         right = new arraylist<integer>(midpoint + 1);      int[] result = new int[b.size()];      (int = 0; < midpoint; i++)         left.set(i, b.get(i));        int x = 0;     (int j = midpoint; j < b.size(); j++)     {         if(x < right.size())             right.set(x, b.get(j));             x++;     }      left = merge_sort(left);     right = merge_sort(right);      result = merge(left, right);     return result; }  public static arraylist<integer> merge(arraylist<integer> left, arraylist<integer> right) {     int lengthresult = left.size() + right.size();     arraylist<integer> result = new arraylist<integer>(lengthresult);     int indexl = 0;     int indexr = 0;     int indexres = 0;      while (indexl < left.size() || indexr < right.size())     {         if(indexl < left.size() && indexr < right.size())         {             if (left.get(indexl) <= right.get(indexr))             {                 result.set(indexres, left.get(indexl));                 indexl++;                 indexres++;             }             else             {                 result.set(indexres, right.get(indexr));                 indexr++;                 indexres++;             }            }         else if (indexl < left.size())         {             result.set(indexres, left.get(indexl));             indexl++;             indexres++;         }         else if (indexr < right.size())         {             result.set(indexres, right.get(indexr));             indexr++;             indexres++;         }     }     return result; } 

remove line

int[] result = new int[b.size()]; 

and change this

list<integer> result = merge(left, right);