code: private int indexOf(int key) {
  		int startIndex = hashIndex(key);
  		int index = startIndex;
  
  		for (;;) {
  			if (values[index] == null) {
  				// It's available, so no chance that this value exists anywhere in the map.
  				return -1;
  			}
  			if (key == keys[index]) {
  				return index;
  			}
  
  			// Conflict, keep probing ...
  			if ((index = probeNext(index)) == startIndex) {
  				return -1;
  			}
  		}
  	}
docs: Locates the index for the given key. This method probes using double hashing.
  
  @param key the key for an entry in the map.
  @return the index where the key was found, or {@code -1} if no entry is found for that key.