public class WhileDemo {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		String t = "ab78%f^fhj*k";
        System.out.println(getLetters(t));
	}
	public static String getLetters(String s){
		int j = 0;
		int len = s.length();
		String letters = "";
		// this double while loop illustrates the difference
		// between && and &, but the simpler code that we wrote
		// on the blackboard using only one while loop was better
		while (j < len){
			// skip over non-letters
			while (j < len & (s.charAt(j) < 'a' || s.charAt(j) > 'z')){
				j++;
			}
			if(j < len){
				//concatenate new letter onto ones already obtained
				letters = letters + s.charAt(j);
			}
			j++;
		}
		return letters;
	}

}