Probleme de string java.

public class StringReplacer {

	/**
	 *  Replaces a substring by another one in a String
	 *
	 * @param text The text where you want to replace a substring
	 * @param currentSubstring The substring to replace
	 * @param newSubstring The new substring
	 * @return The original text with all occurences of currentSubstring replaced by newSubstring
	 * @exception  ReplacerException  Exception which is thrown if the substring you ask to replace is longer than the whole text
	 * @author Philippe Fery
	 * @created June 04, 2002
	 */
	public static String replace(String text, String currentSubstring, String newSubstring) throws ReplacerException
	{
		int repeat = text.length() - currentSubstring.length();
		if (repeat >= 0)
		{
			for (int i = 0; i < repeat; i++)
			{
				String testSubstring = text.substring(i, i + currentSubstring.length());
				if (testSubstring.equals(currentSubstring))
				{
					text = text.substring(0, i) + newSubstring + text.substring(i + currentSubstring.length());
					i += newSubstring.length();
				}
			}
		}
		else
		{
			throw replacerException;
		}
		return text;
	}


	/**
	 *  ReplacerException is an Exception which is thrown if the substring you ask
	 *  to replace is longer than the whole text.
	 *
	 * @author     Philippe Fery
	 * @created    June 04, 2002
	 */
	static class ReplacerException extends Exception
	{
		public String getMessage()
		{
			return "The substring to search is longer than the text";
		}
	}

	private final static ReplacerException replacerException = new ReplacerException();

	public static void main(String args[]){
		try {
			String str = StringReplacer.replace("abc\'def\'ghi\'\'jkl","\'","'");
			System.out.println(str);
		} catch (ReplacerException e) {
			e.printStackTrace();
		}
	}
}