code: @SuppressWarnings("unchecked")
      public V put(final int key, final V value)
      {
          final V val = (V)mapNullValue(value);
          requireNonNull(val, "value cannot be null");
  
          V oldValue = null;
          @DoNotSub final int mask = values.length - 1;
          @DoNotSub int index = Hashing.hash(key, mask);
  
          while (null != values[index])
          {
              if (key == keys[index])
              {
                  oldValue = (V)values[index];
                  break;
              }
  
              index = ++index & mask;
          }
  
          if (null == oldValue)
          {
              ++size;
              keys[index] = key;
          }
  
          values[index] = val;
  
          if (size > resizeThreshold)
          {
              increaseCapacity();
          }
  
          return unmapNullValue(oldValue);
      }
docs: Overloaded version of {@link Map#put(Object, Object)} that takes a primitive int key.
  
  @param key   for indexing the {@link Map}
  @param value to be inserted in the {@link Map}
  @return the previous value if found otherwise null