Printing all possible subsets of a list

Question

I have a List of elements (1, 2, 3), and I need to get the superset (powerset) of that list (without repeating elements). So basically I need to create a List of Lists that

Answer 1

This is the simple function can be used to create a list of all the possible numbers generated by digits of all possible subsets of the given array or list.

void SubsetNumbers(int[] arr){
    int len=arr.length;
    List list=new ArrayList();
    List list1=new ArrayList();
    for(int n:arr){
        if(list.size()!=0){
            for(int a:list){
                list1.add(a*10+n);
            }
            list1.add(n);
            list.addAll(list1);
            list1.clear();
        }else{
            list.add(n);
        }
    }
    System.out.println(list.toString());
}