Find All Permutations of a String

public class StringPermutation {

	public void permute(String str, int start, int stop) {
	
		if (stop == start) {
		  System.out.println(str);
		  return;
		}
		for(int i=start;i <= stop; i++) {
			str = swap(str, start, i);
			permute(str, start+1, stop);
			
		}
	}

	public String swap(String str, int a, int b) {
	  char[] chars = str.toCharArray();
	  char temp = chars[a];
	  chars[a] = chars[b];
	  chars[b] = temp;
	  
	  return String.valueOf(chars);
	}


	public static void main(String args[]) {
	   StringPermutation perm = new StringPermutation();
	   if (args.length < 1) {
	      System.out.println("Needs string argument");
	      return;
	   }
	   String str = args[0];
	   System.out.println("Processing " + str + " of length  " + str.length());
	   perm.permute(str, 0, str.length()-1);
	}
}