Generating Combinations

The algorithm for this is very similar to the algorithm for generating permutations.

Algorithm:
1. Remove Item i from elements and put in output array
2. Display Output
3. Generate combinations for rest of the array

public void combine(String str){
  int l=str.length();  
  StringBuilder out=new StringBuilder();
  char []in=str.toCharArray();
  doCombine(in,out,l,0);
 }
 private void doCombine(char[] in, StringBuilder out, int n, int start){
  for(int i=start;i<n;i++){   
   out.append(in[i]);
   System.out.println(out);
   if(i<n)
    doCombine(in, out, n, i+1);
   
   out.setLength(out.length()-1);
  }
 }