Combination/Matrix Generation Automation?

Question

Hi everyone:
The current problem in front of me is that I have a set of string elements, say N of them, while the task is to automatically generate ALL combinations with length ranging from 1 to (N-1). If, for example, given 'a, b, c, d', the following output is desirable:
a, b, c, d, e, ab, ac, ad, bc, bd, cd, abc, abd, acd, bcd
I attempted nested loops but so far unsuccessful unfortunately. How can this be done? Many thanks in advance!!
Regards,

Answer 1

Thanks for the URL. It lists what I basically want to
achieve...except the order should not matter in my
case, i.e. 'abc' = 'cba' and only 1 of the two should
stay. Can you please give out a bit more hints on
adjustment of the CombinationGenerator source code on
that link?Look at the first example on the link where the class is used. I tested using it for getting combinations of three characters with abcdef as input String. Here's the output I get.
abc
abd
abe
abf
acd
ace
acf
ade
adf
aef
bcd
bce
bcf
bde
bdf
bef
cde
cdf
cef
def
I think that's what you are expecting.
public class TestCombo {
    public static void main(String[] args) {
        char[] elements = {'a', 'b', 'c', 'd', 'e', 'f'};
        int[] indices;
        CombinationGenerator x = new CombinationGenerator (elements.length, 3);
        StringBuffer combination;
        while (x.hasMore ()) {
            combination = new StringBuffer ();
            indices = x.getNext ();
            for (int i = 0; i < indices.length; i++) {
                combination.append (elements[indices]);
System.out.println (combination.toString ());