this,
it refers to the current instance of the inner class.
To refer to the instance of the outer class from the
inner class, this must be qualified
by the name of the outer class.
this from inner class1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 |
// ShadowThis.java -- Illustrate shadowing of this.
// Fred Swartz - 2003 - Jun
class ShadowThis {
public static void main(String[] args) {
ShadowThis st = new ShadowThis();
st.testOuter();
}//end main
private void testOuter() {
System.out.println(this);
InnerShadowThis ist = new InnerShadowThis();
ist.testInner();
}//end test
class InnerShadowThis {
void testInner() {
System.out.println(this);
System.out.println(ShadowThis.this);
}
}//end class InnerShadowThis
}//end class ShadowThis
|
ShadowThis@601bb1 ShadowThis$InnerShadowThis@ea2dfe ShadowThis@601bb1
this might be used. A common
situation is to implement an action listener as an
inner class of a JPanel. If the listener wants to
display a dialog (eg, a JFileChooser), it may tell
which component to center the dialog over.
The component is exactly the outer this.
For example, this is from an inner class listener that
wants to center a file dialog over the current TestGUI
panel.
int retval = fileChooser.showOpenDialog(TestGUI.this);
Some IDEs put no code in an inner class listener except a call to
an outer method to process the action. The same code could be used,
but the need to refer to the outer this
is no longer necessary.