J2SE里面关闭当前窗体并且释放内存

setDefaultCloseOperation

public void setDefaultCloseOperation(int operation)

Sets the operation that will happen by default when the user initiates a "close" on this frame. You must specify one of the following choices:

* DO_NOTHING_ON_CLOSE (defined in WindowConstants): Don't do anything; require the program to handle the operation in the windowClosing method of a registered WindowListener object.
* HIDE_ON_CLOSE (defined in WindowConstants): Automatically hide the frame after invoking any registered WindowListener objects.
* DISPOSE_ON_CLOSE (defined in WindowConstants): Automatically hide and dispose the frame after invoking any registered WindowListener objects.
* EXIT_ON_CLOSE (defined in JFrame): Exit the application using the System exit method. Use this only in applications.

The value is set to HIDE_ON_CLOSE by default. Changes to the value of this property cause