elk-util-parent/elk-util-collections/src/main/java/org/semanticweb/elk/util/collections/LinearProbing.java
static <E> boolean add(E[] d, E e) {
		int pos = getPosition(d, e);
		if (d[pos] == null) {
			d[pos] = e;
			return true;
		}
		// else the element is already there
		return false;
	}
static <E> boolean add(E[] d, E e) {
		int pos = getPosition(d, e);
		if (d[pos] == null) {
			d[pos] = e;
			return true;
		}
		// else the element is already there
		return false;
	}
Adds the element to the set represented by given data array, if it did
not contain there already.

@param d
the elements of the set
@param e
the element to be added to the set
@return {@code true} if the set has changed (the element is added),
{@code false} otherwise