docs: public static String repeat(String string, int count) {
          requireNonNull(string);
  
          if (count <= 1) {
              if (count < 0) {
                  throw new IllegalArgumentException("invalid count: " + count);
              }
              return (count == 0) ? "" : string;
          }
  
          // IF YOU MODIFY THE CODE HERE, you must update StringsRepeatBenchmark
          final int len = string.length();
          final long longSize = (long) len * (long) count;
          final int size = (int) longSize;
          if (size != longSize) {
              throw new ArrayIndexOutOfBoundsException("Required array size too large: " + longSize);
          }
  
          final char[] array = new char[size];
          string.getChars(0, len, array, 0);
          int n;
          for (n = len; n < size - n; n <<= 1) {
              System.arraycopy(array, 0, array, n, n);
          }
          System.arraycopy(array, 0, array, n, size - n);
          return new String(array);
      }