Java Swing popup visibility

Why a popup created like this is shown in front of all windows applications with JRE 1.6.0_18 but it doesn't using 1.6.0_03 ?

PopupFactory popupFactory = new PopupFactory();
    Popup popup= popupFactory.getPopup(null,new JPanel(),200,200开发者_如何学JAVA);
    popup.show();

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Sounds like "something" has changed between those JRE versions. They have either fixed a bug or introduced a new one. I don't think there's more magic than that.

If you are very interested in knowing what exactly has changed, you can check out this link: http://java.sun.com/javase/6/webnotes/ReleaseNotes.html