Design Compressed String Iterator

Design and implement a data structure for a compressed string iterator. It should support the following operations: next and hasNext.

The given compressed string will be in the form of each letter followed by a positive integer representing the number of this letter existing in the original uncompressed string.

next() - if the original string still has uncompressed characters, return the next letter; Otherwise return a white space.
hasNext() - Judge whether there is any letter needs to be uncompressed.

Note:
Please remember to RESET your class variables declared in StringIterator, as static/class variables are persisted across multiple test cases. Please see here for more details.

Example:

StringIterator iterator = new StringIterator("L1e2t1C1o1d1e1");

iterator.next(); // return 'L'
iterator.next(); // return 'e'
iterator.next(); // return 'e'
iterator.next(); // return 't'
iterator.next(); // return 'C'
iterator.next(); // return 'o'
iterator.next(); // return 'd'
iterator.hasNext(); // return true
iterator.next(); // return 'e'
iterator.hasNext(); // return false
iterator.next(); // return ' '

 public class StringIterator {
     int i;
     String[] arr;
     int[] counts;

     public StringIterator(String str) {
         arr = str.split("\\d+");
         counts = Arrays.stream(str.substring().split("[a-zA-Z]+")).mapToInt(Integer::parseInt).toArray();
     }

     public char next() {
         if (!hasNext()) {
             return ' ';
         }
         char ch = arr[i].charAt();
         counts[i]--;

         if (counts[i] == ) {
             ++i;
         }
         return ch;
     }

     public boolean hasNext() {
         if (i == arr.length) {
             return false;
         }
         return true;
     }
 }