public class CombinationIterator<T>
extends Object
implements Iterator<List<T>>

This iterates through every combination of a list of arrays. For example:

List<String[]> input = new ArrayList<>();
input.add(new String[] {"1", "2", "3"});
input.add(new String[] {"apple", "orange"});
input.add(new String[] {"X"});
CombinationIterator<String> iter = new CombinationIterator<>(input);
while(iter.hasNext()) {
        System.out.println(iter.next());
}

This code will output this list:

• "1", "apple", "X"
• "1", "orange", "X"
• "2", "apple", "X"
• "2", "orange", "X"
• "3", "apple", "X"
• "3", "orange", "X"

It helps to visualize this as a slot machine, where "1", "2", "3" are vertically stacked as one place/slot in the machine. "apple", "orange" is the next slot, and "X" is always the 3rd slot.