Combinations.java

public class Combinations 
{
    static void printCombinations(char[] sequence, int N) 
    {
        char[] data = new char[N];
        for (int r = 0; r < sequence.length; r++)
            combinations(sequence, data, 0, N - 1, 0, r);
    }
 
    static void combinations(char[] sequence, char[] data, int start, int end,
            int index, int r) 
    {
 
        if (index == r) 
        {
            for (int j = 0; j < r; j++)
                System.out.print(data[j] + " ");
            System.out.println();
        }
 
        for (int i = start; i <= end && ((end - i + 1) >= (r - index)); i++) 
        {
            data[index] = sequence[i];
            combinations(sequence, data, i + 1, end, index + 1, r);
        }
    }
 
    public static void main(String args[]) 
    {
        char[] sequence = { 'a', 'b', 'c', 'd', 'e' };
        System.out.print("The combinations are: ");
        printCombinations(sequence, sequence.length);
    }
}