Return Keypad

//Given an integer n,using phone keypad,find the possible strings that can be made using digits of input n

public class Keypad {
	
	public static String keypadHelper(int n) {
		if(n==1)
			return "";            // possibilities in a mobile keypad
		else if(n==2)
			return "abc";
		else if(n==3)
			return "def";
		else if(n==4)
			return "ghi";
		else if(n==5)
			return "jkl";
		else if(n==6)
			return "mno";
		else if(n==7)
			return "pqrs";
		else if(n==8)
			return "tuv";
		else
			return "wxyz";
			
				// String arr[]={"","","abc","def"....};      another option for creating the possibilities
		//return arr[n];
		
	}
	public static String[] keypad(int num) {

		
	if(num==0)        // base case
	{
		String[] output= {""};
		return output;
	}
	
	
	String[] smalloutput=keypad(num/10);      // string array to store recursion's answer
	
	String ans=keypadHelper(num%10);
	
	String output[]=new String[smalloutput.length*ans.length()];          // string to store final answer
	
	int k=0;
	for(int i=0;i<ans.length();i++)
	{
		for(int j=0;j<smalloutput.length;j++)
		{
			output[k]=smalloutput[j]+ans.charAt(i);
			k++;
		}
	}
	
	return output;	
	}
	

	public static void main(String[] args) {
		// TODO Auto-generated method stub
int num=23;
String[] a=keypad(num);
for(int i=0;i<a.length;i++)
System.out.println(a[i]);

	}
}