private void handleDuplicate(T t) {
		if (allowDuplicates) {
			return;
		}

		int itemIndex = historyStack.search(t);
		if (itemIndex == -1) {
			return;
		}
		historyStack.remove(itemIndex);
	}
Returns the number of items in this history list

@return the number of items in this history list
Ghidra/Framework/Generic/src/main/java/util/HistoryList.java