import java.awt.*;

public class Attn {

    public static void main(String[] args) throws InterruptedException {
        Frame f = new Frame();
        f.setBounds(100, 100, 100, 100);
        f.setVisible(true);
        f.setState(Frame.ICONIFIED);
        Thread.sleep(1000);
        Taskbar tb = Taskbar.getTaskbar();
        if (tb.isSupported(Taskbar.Feature.USER_ATTENTION_WINDOW)) {
            tb.requestWindowUserAttention(f);
        }
    }
}