Algoritim to print all combinations of array in order.

combPowerSet.java

package combinations;

import java.util.*;
import java.math.*;

public class combPowerSet {

     //printing the charachters as per the number sent.
     void printNumber(int number, char [] items)
        {
            String digitString = Integer.toString(number);
            char [] digitStringArray = digitString.toCharArray();
            int length = digitStringArray.length;
            for ( int i=0; i<length; i++)
            {
                System.out.print(items[Character.getNumericValue(digitStringArray[i])-1]);
            }
            System.out.println();
        }

    //checking if the number follows the required pattern.
    boolean checkCondition(int number, int itemSize)
    {
        boolean validNumber = true;
        String digitString = Integer.toString(number);
        char [] digitStringArray = digitString.toCharArray();
        int length = digitStringArray.length;
        for ( int i=0; i<length; i++)
        {
            for( int j = i+1; j < length; j++)
            {
                int x = Character.getNumericValue(digitStringArray[i]);
                int y = Character.getNumericValue(digitStringArray[j]);             

                if (x > itemSize-1 || y > itemSize || x > y  || x==y)
                {
                    validNumber = false;
                    break;
                }               
            }
            if (validNumber == false) break;
         }
        return validNumber;     
    }


    void printCombinations(char [] items)
    {
        double maxDigit = 0; 
        int itemSize = items.length;
        for(int i=1; i<=itemSize; i++)
        {
            maxDigit = maxDigit + i*Math.pow(10,itemSize-i);
        }


        for(int x=12; x<=maxDigit; x++)
        {
            if(checkCondition(x, itemSize))
            {
                printNumber(x, items);
            }
        }
    }

    public static void main(String [] args)
    {
        char [] arr = { 'a','b', 'c','d', 'e'};
        combPowerSet obj = new combPowerSet();
        obj.printCombinations(arr);     

    }
 }