CareerCup

The trick is to implement PrintInt(int num) to work on the number range [999,...,0]. Then keep reuse this code on every 10^3 such as Million and Thousand (Please see PrintIntWrp( ) the wrapper function).
Similarly for PrintInt(0<=num<=999) will implement by keep dividing by ten and try to print the num%10. We will work this backward until deduct num down to zero; The special cases, of cause, is the "teens" and "tys" which the tricks in arrays w[], z[] plus the implementation in PrintIntImp(int num) will address this requirement.

String x[] = {"","ty","hundred","thousand","million","billion"};
	String y[] = {"one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};
	String z[] = {"ten","eleven","twelve","thirteen","fourteen","fifteen","sizteen","seventeen","eighteen","nineteen"};
	String w[] = {"","twen","thir","for","fif","six","seven","eigh","nin",""};
	
	
	protected stringtest (){}
	public static stringtest instance(){
		return new stringtest();
	}
	public void printIntWrp(int num){
		StringBuffer buf = new StringBuffer();
		int index = (num>999?3:0);
		while(num > 0){
			String temp = num>999?x[index++]+" ":"";
			temp = temp+printInt(num % 1000);
			buf.insert(0, temp);
			num /= 1000;
		}
		System.out.print(buf.toString());
	}
	
	protected StringBuffer printInt(int num){ //will work for 999,...,0
		StringBuffer bf = new StringBuffer();
		int lak = 0;
		while(num > 0){
			printIntImp(num,bf,lak++);
			num /= 10;
		}
		//System.out.print(bf.toString());
		return bf;
	}
	
	protected void printIntImp(int num, StringBuffer bs, int lak){
		//base case
		if(lak == 0){
			if((num / 10 % 10) == 1) // 10,11,...,19
				bs.append(z[num%10]);
			else
				bs.append(y[num%10-1]);
			return;
		}						
		if(lak == 1) // 10,11,...,19 <already taken care of>
		{
			if(num % 10 != 1) //skip 10,11,...,19
			{
				bs.insert(0, (w[num%10-1]+x[lak])+" ");
			}else;
		}else{
			bs.insert(0, (y[num%10-1]+x[lak])+" ");
		}
	}
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		stringtest st = stringtest.instance();
		st.printIntWrp(122817);
	}

Create a map of num[1] = "one" ...
num[3] = "three"
......
num[9]
num[100]="
num[1000] =
while(num
{
print num[i%10];
}