arrayList Method

A method that creates a total of "n: elements (all different if yes), their combinations of 1-2-3 .... n without repetition
Example:
Entry:
N = {a, b, c}
Comb.1: a | b | c
Comb.2: ab | bc | ac
Comb.3: abc

this I did so far please help!


String combine(ArrayLi st<Integer> a, String b){
String c="";
if(b.length()== a.size()){
System.out.prin tln(b); //found a combo
return "";
}
//append characters to string b
for(int x=0;x<a.size(); x++){
c=b+((Integer)a .get(x)).intVal ue();
c+=combine(a,c) ;
}
return c;
}