Java™ How To Program (Early Objects), Tenth Edition

Returning Window Resources to the System

By default, when the user closes a JFrame window, it’s hidden (i.e., removed from the screen), but you can control this with JFrame method setDefaultCloseOperation. Interface WindowConstants (package javax.swing), which class JFrame implements, declares three constants—DISPOSE_ON_CLOSE, DO_NOTHING_ON_CLOSE and HIDE_ON_CLOSE (the default)—for use with this method. Some platforms allow only a limited number of windows to be displayed on the screen. Thus, a window is a valuable resource that should be given back to the system when it’s no longer needed. Class Window (an indirect superclass of JFrame) declares method dispose for this purpose. When a Window is no longer needed in an application, you should ...