code: public float putAndGet(final int key, final float value) {
          int index = findInsertionIndex(key);
          float previous = missingEntries;
          boolean newMapping = true;
          if (index < 0) {
              index = changeIndexSign(index);
              previous = values[index];
              newMapping = false;
          }
          keys[index]   = key;
          states[index] = FULL;
          values[index] = value;
          if (newMapping) {
              ++size;
              if (shouldGrowTable()) {
                  growTable();
              }
              ++count;
          }
          return previous;
      }
docs: Put a value associated with a key in the map.
  @param key key to which value is associated
  @param value value to put in the map
  @return previous value associated with the key