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I am looking for feedback on a solution to the following problem posed from a book that I'm working through (Java: How To Program, 9th Edition):

Write an application that reads a five-letter word from the user and produces every possible three-letter string that can be derived from the letters of that word. For example, the three-letter words produced from the word "bathe" include "ate," "bet," "tab," "hat," "the," and "tea."

I have a sneaking suspicion that I've over complicated things. Is my code easy to understand? I'm a rookie coder still going over the basics.

import java.util.Scanner;

public class ThreeLetterStrings {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner( System.in );
        System.out.println( "Please enter a five letter word" ); 
        String userInput = sc.nextLine();           // get input
        int wordLength = userInput.length();       // get length of string in question
        char[] charArray = new char[ wordLength ];
        int stem = 0;       // stem being the 2nd letter after the first - b(a)the or ba(t)he
        int scan = 0;       // scan count for while loop
        boolean stamp;

        for( int i = 0; i < charArray.length; i++ )     // feed string into char array
        {
            charArray[ i ] = userInput.charAt( i );
        }

        for( int startLetter = 0; startLetter < wordLength; startLetter++ )
        {
            for( int stemLetter = 1; stemLetter < wordLength; stemLetter++ )
            {
            stem = startLetter + stemLetter;
            if( stem >= wordLength )
                stem = stem - wordLength;
            scan = 0;       // reset scan count after walk for loop
                for( int walk = 0; walk < wordLength - 2; walk++ )
                {
                    System.out.printf( "%c", charArray[ startLetter ] );
                    System.out.printf( "%c", charArray[ stem ] );
                    stamp = false;      // determines whether a character was printed

                    while( stamp == false )
                    {
                        if( scan == startLetter || scan == stem  )
                        {
                            scan++;
                        }
                        else
                        {
                            System.out.printf( "%c", charArray[ scan ] );
                            stamp = true;
                            System.out.println();
                            scan++;
                        }
                    } // end while
                } // end walk for
            } // end stemLetter for
        } // end startLetter for    
    }
}
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Your program can be simplified to something like this:

System.out.println("Please enter a five letter word"); 
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();

for (int i = 0; i < input.length(); i++) {             // pos. of 1st letter
    for (int j = 0; j < input.length(); j++) {         // pos. of 2nd letter
        for (int k = 0; k < input.length(); k++) {     // pos. of 3rd letter
            if (i == j || i == k || j == k) continue;  // any letter taken twice? -> skip
            System.out.printf("%c%c%c\n", input.charAt(i), input.charAt(j), input.charAt(k));
        }
    }
}

Some more pointers:

  • while this works for combinations of three letters, for combinations of more letters (or arbitrary numbers of letters) you should use some sort of recursive function
  • you might want to check whether the entered word is actually five letters long
  • before printing, you could store the three-letter-words in a Set<String> to filter out duplicates
  • the question is a bit unclear whether it's about three-letter strings or three-letter words; in the latter case you might want to get some dictionary of valid three-letter words and check whether the combinations are in that list
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  • \$\begingroup\$ Wow! Great stuff a triple nested loop. This is perfect, thank you tobias_k, this is really much simpler. I'm still a couple of chapters away from recursion and collections; still earning my wings. Thanks again, very helpful. \$\endgroup\$ – cryptocurry Jul 23 '13 at 10:47

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