int deltaLength= event.getText().length() - event.getLength();
int deltaLength= (event.getText() == null ? 0 : event.getText().length()) - event.getLength();
	public void update(DocumentEvent event) {		int deltaLength= event.getText().length() - event.getLength();		Position[] positions= getPositions(event.getDocument());		TypedPosition currentPosition= (TypedPosition) findCurrentPosition(positions, event.getOffset());		// document change outside positions		if (currentPosition == null) {						for (int i= 0; i != positions.length; i++) {				TypedPosition position= (TypedPosition) positions[i];				int offset= position.getOffset();								if (offset >= event.getOffset())					position.setOffset(offset + deltaLength);			}					// document change within a position		} else {			int length= currentPosition.getLength();				for (int i= 0; i != positions.length; i++) {				TypedPosition position= (TypedPosition) positions[i];				int offset= position.getOffset();								if (position.equals(currentPosition)) {					position.setLength(length + deltaLength);									} else if (offset > currentPosition.getOffset()) {					position.setOffset(offset + deltaLength);				}			}				}	}