Programming Challenge 1 - StringZipper

/**
 * @Author: FamiHug at FAMILUG
 * @Version: 1.0 Tue Aug  2 23:53:23 ICT 2011
 */

public class PRC01CompressString {
    public static void main(String[] args)
    {
        StringZipper sz = new StringZipper();

        System.out.println("Programming Challenger 01 - FAMILUG\u2122 \n");

        String input = "AAABBCAABDDAFF";
        System.out.println("Input: " + input + "\n");

        String compressed = sz.compress(input);
        System.out.println("Compressed: " + compressed);

        String extracted = sz.extract(compressed);
        System.out.println("Extracted: " + extracted);
    }
}

class StringZipper {
    public String compress(String input)
    {
        int charCounter = 1;
        char currentChar = input.charAt(0);
        char previousChar;
        StringBuffer compressedString = new StringBuffer();

        for(int i = 1; i < input.length(); i++) {
            previousChar = currentChar;
            currentChar = input.charAt(i);
            if(currentChar == previousChar) {
                charCounter++;
            }
            else {
                if(charCounter != 1) {
                    //System.out.print(charCounter + "" + previousChar);
                    compressedString.append(charCounter);
                    compressedString.append(previousChar);
                }
                else compressedString.append(previousChar);

                charCounter = 1;
            }
        }
        compressedString.append(charCounter);
        compressedString.append(currentChar);
        compressedString.append("\n");
        //System.out.println(charCounter + "" + currentChar);
        return compressedString.toString();
    }

    public String extract(String compressedString) {
        int loopTimes = 0;
        int currentChar;
        StringBuffer extracted = new StringBuffer();

        for(int i = 0; i < compressedString.length(); i++)
        {
            if(Character.isDigit(compressedString.charAt(i))) loopTimes = loopTimes * 10 + Character.digit(compressedString.charAt(i), 10);
            else
            {
                if(loopTimes == 0) loopTimes = 1;
                for(int j = 0; j < loopTimes; j++) {
                    //System.out.print(compressedString.charAt(i));
                    extracted.append(compressedString.charAt(i));
                }
                loopTimes = 0;
            }
        }
        //System.out.println();
        extracted.append("\n");
        return extracted.toString();
    }

}