code: public double get(int i) {
          for (Entry e : array) {
              if (e.i == i) {
                  return e.x;
              }
          }
  
          return 0.0;
      }
docs: Returns the value of i-th entry.
  @param i the index of entry.
  @return the value of entry, 0.0 if the index doesn't exist in the array.