code: public int keyOf(double value) {
  	//returns the first key found; there may be more matching keys, however.
  	int i = indexOfValue(value);
  	if (i<0) return Integer.MIN_VALUE;
  	return table[i];
  }
docs: Returns the first key the given value is associated with.
  It is often a good idea to first check with {@link #containsValue(double)} whether there exists an association from a key to this value.
  Search order is guaranteed to be <i>identical</i> to the order used by method {@link #forEachKey(IntProcedure)}.
  
  @param value the value to search for.
  @return the first key for which holds <tt>get(key) == value</tt>;
  returns <tt>Integer.MIN_VALUE</tt> if no such key exists.