List All Possible Word Combinations From A String Of Letters - Java

I recently was given a programming assignment to list all word combinations given an input of letters.

Here was my algorithm:

Function(string, rest):
For each letter in the input
append the letter to string
add the string to a hashset
Function(string + new appended letter, rest - appended letter)
remove the appendation

//Adds every combination of the letters to a hashset
 private void getWords(StringBuilder string, StringBuilder append)
 {
  //Base Case
  if(append.toString().isEmpty())
  {
   return;
  }
  
  //Recursive case
  //For each letter in append, append to string then recurse with string and append
  //without the appended letter
  for(int i = 0; i < append.length(); i++)
  {
   string.append(append.charAt(i));
   set.add(string.toString());
   getWords(string, new StringBuilder(append).deleteCharAt(i));
   string.deleteCharAt(string.length()-1);
  }
 }