Combination of a string

Algorithm :

Step 1: Add the String to the combination results.
 Step 2: If the String has just one character in it, 
        then stop the current line of execution.
 Step 3: Create new sub-words from the String by removing one letter at a time. 
        If the String is "ABCD", form sub-words like "BCD", "ACD", "ABD", "ABC"
 Step 4: For each of the sub-word, go to Step 1

Java program :

 import java.util.HashSet;
import java.util.Set;

/**
 * A simple program that generates all possible combinations for a given String
 * using recursion.
 */
public class StringCombinations {
 // A set to hold the generated combination results.
 private Set<String> combinations = new HashSet<String>();

 /**
  * The constructor.
  * 
  * Simply makes a call to the generate method to generate all the possible
  * combinations of the String "wxyz"
  */
 public StringCombinations(String sInputString) {
  generate(sInputString);
  System.out.println("*** Generated " + combinations.size()
    + " combinations ***");
  System.out.println(combinations);
 }

 /**
  * The recursive method does the work of generating all the possible
  * combinations for a given String.
  */
 public void generate(String word) {
  // Add this word to our combination results set
  combinations.add(word);

  // If the word has only one character we break the recursion
  if (word.length() == 1) {
   combinations.add(word);
   return;
  }
  // Go through every position of the word
  for (int i = 0; i < word.length(); i++) {
   // Remove the character at the current position
   // all call this method with that String (Recursion!)
   generate(word.substring(0, i) + word.substring(i + 1));
  }
 }

 /**
  * Entry point to this program. Instantiates the StringCombinations program.
  * 
  */
 public static void main(String args[]) {
  String sInputString = "abcd";
  new StringCombinations(sInputString);
 }

}