How to generate the power-set of a given List?

Question

I\'m trying to generate a collection of all 2^N - 1 possible combinations of a given List of length N. The collection will map the number of elements in a combination to an

Answer 1

public static List getCombinationsLists(List elements)
{
    
    //return list with empty String
    if(elements.size() == 0){
        List allLists = new ArrayList();
        allLists.add("");
        return allLists ;
    }

    String first_ele = elements.remove(0);
    List rest = getCombinationsLists(elements);
    int restsize = rest.size();
    //Mapping the first_ele with each of the rest of the elements.
    for (int i = 0; i < restsize; i++) {
        String ele = first_ele + rest.get(i);
        rest.add(ele);
    }
   
    return   rest;
}

This Power set is one of the exercise in the book SICP "Structure and Interpretation of Computer Programming".Every Programmer should read it.