code: public void append(int key, long value) {
          if (mSize != 0 && key <= mKeys[mSize - 1]) {
              put(key, value);
              return;
          }
  
          int pos = mSize;
          if (pos >= mKeys.length) {
              growKeyAndValueArrays(pos + 1);
          }
  
          mKeys[pos] = key;
          mValues[pos] = value;
          mSize = pos + 1;
      }
docs: Puts a key/value pair into the array, optimizing for the case where
  the key is greater than all existing keys in the array.