Here's the test case:

import java.awt.*;

public class FrameTest extends Frame {
    public void paint(Graphics g) {
        g.setColor(Color.RED);
        g.fillRect(0, 0, getWidth(), getHeight());
    }

    public void update(Graphics g) {
        paint(g);
    }

    public static void main(String[] args) {
        Frame f = new FrameTest();
        f.setBounds(0, 0, 200, 200);
        f.show();
    }
}

Try resizing the frame and as it gets bigger and bigger the flickering is
more noticable. I couldn't reproduce this MToolkit.