Any Commons all substrings function?

I'm wondering if there's a library function (or why StringUtils in Apache Commons doesn't have it?) that for a String calculates all the substrings. For "abcde" it retuns "a开发者_如何学JAVA", "ab", "b", "abc", "bc", "c", "abcd", "bcd", "cd","d", "abcde", "bcde", "cde", "de", "e".

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I don't believe there's a library function, but it would be extremely easy to just roll one youself:

public ArrayList<String> getAllSubstrings(String s)
{
   ArrayList<String> toReturn = new ArrayList<String>();
   for (int i = 0; i < s.length(); i++)
      for (int j = i + 1; j < s.length(); j++)
         toReturn.add(s.substring(i, j));
}

Remember though, that there will be a number of permutations equal to 1+2+3+4+...+s.length

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I don't think AndyPerfect's will work correctly. The second loop bound needs to be <= instead of just <.

public static ArrayList<String> getPowerSet(String original) {
       ArrayList<String> toReturn = new ArrayList<String>();

       toReturn.add("");

       for (int i = 0; i < original.length(); i++) {
          for (int j = i + 1; j <= original.length(); j++) {
             toReturn.add(original.substring(i, j));
          }
       }

       return toReturn;
    }

Note that you can remove that first add() if you don't want the empty substring included.

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Sounds computational intensive. Think of all the permutations you would have with whole sentences.

That and they probably figured if somebody needed something that wasn't something needed on a regular basis.

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public static ArrayList getPowerSet(String original) { ArrayList toReturn = new ArrayList();

   toReturn.add("");

   for (int i = 0; i < original.length(); i++) {
      for (int j = i + 1; j <= original.length(); j++) {
         toReturn.add(original.substring(i, j));
      }
   }

   return toReturn;
}

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public static ArrayList<String> getPowerSet(String original) {
       ArrayList<String> toReturn = new ArrayList<String>();

       toReturn.add("");

       for (int k = 0; k < original.length(); k++) {
          for (int j = k + 1; j <= original.length(); j++) {
             toReturn.add(original.substring(k, j));
          }
       }

       return toReturn;
    }