String content= document.get(fReplacementPosition.getOffset(), fReplacementPosition.getLength());
String content= document.get(fReplacementPosition.getOffset(), offset - fReplacementPosition.getOffset());
	public boolean validate(IDocument document, int offset, DocumentEvent event) {		try {			String content= document.get(fReplacementPosition.getOffset(), fReplacementPosition.getLength());			if (fReplacementString.startsWith(content))				return true;		} catch (BadLocationException e) {			// ignore concurrently modified document		}		return false;	}