ADDITIONAL SYSTEM INFORMATION :
MacBook Pro 2017, macOS 10.14.2, tested with JDK 1.8.0_192, JDK 11.0.1, and JDK 12 (early access release)

A DESCRIPTION OF THE PROBLEM :
When running any splash screen using java.awt.SplashScreen, it always stays on top of all windows of all applications despite clicking another window. This does not occur on Windows.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the below source code as a jar or in an IDE with the VM argument "-splash:pathToImage" with pathToImage being a path to a downloaded copy of the image at the following link: https://i.imgur.com/snPOG2S.gif

Alternatively, here's a link to a compiled jar with the given code: https://github.com/Jorl17/jar2app/files/1456251/SplashDemo.jar.zip.

It already has the image internally and was compiled with the following line in the manifest "SplashScreen-Image: splash.gif", so the VM argument isn't required.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The SplashScreen hides under overlapping windows if they are focused
ACTUAL -
The SplashScreen hides for a split second before forcing itself on top of all overlapping windows

---------- BEGIN SOURCE ----------
/*
 * Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of Oracle or the names of its
 * contributors may be used to endorse or promote products derived
 * from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package splash;

import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Frame;
import java.awt.Graphics2D;
import java.awt.Menu;
import java.awt.MenuBar;
import java.awt.MenuItem;
import java.awt.RenderingHints;
import java.awt.SplashScreen;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

public class SplashDemo extends Frame implements ActionListener {
    private static final long serialVersionUID = 1L;

    private static void renderSplashFrame(Graphics2D g, int frame) {
        final String[] comps = {"foo", "bar", "baz"};
        g.setComposite(AlphaComposite.Clear);
        g.fillRect(120, 140, 200, 40);
        g.setPaintMode();
        g.setColor(Color.BLACK);
        g.drawString("Loading " + comps[(frame / 5) % 3] + "...", 120, 150);
    }

    private SplashDemo() {
        super("SplashScreen demo");
        setSize(300, 200);
        setLayout(new BorderLayout());
        Menu m1 = new Menu("File");
        MenuItem mi1 = new MenuItem("Exit");
        m1.add(mi1);
        mi1.addActionListener(this);
        this.addWindowListener(closeWindow);

        MenuBar mb = new MenuBar();
        setMenuBar(mb);
        mb.add(m1);
        final SplashScreen splash = SplashScreen.getSplashScreen();
        if(splash == null) {
            System.out.println("SplashScreen.getSplashScreen() returned null");
            return;
        }
        Graphics2D g = splash.createGraphics();
        if(g == null) {
            System.out.println("g is null");
            return;
        }
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        for(int i = 0; i < 100; i++) {
            renderSplashFrame(g, i);
            splash.update();
            try {
                Thread.sleep(90);
            }
            catch(InterruptedException ignored) {}
        }
        splash.close();
        setVisible(true);
        toFront();
    }

    @Override
    public void actionPerformed(ActionEvent ae) {
        System.exit(0);
    }

    private static WindowListener closeWindow = new WindowAdapter() {
        @Override
        public void windowClosing(WindowEvent e) {
            e.getWindow().dispose();
        }
    };

    public static void main(String[] args) {
        new SplashDemo();
    }
}
---------- END SOURCE ----------

FREQUENCY : always