java - Auto resize a JPanel in multiples of 50 -

i need design interface have innerpanel resizes outterpanel. ok, problem need innerpanel resize in multiples of 50.

so, if outterpanel has 50px, innerpanel has 50px. if outterpanel resizes 80px, innerpanel stays sized @ 50px. when outterpanel gets resized 110px, innerpanel goes 100px.

thanks in advance!

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edit: suggested, i'm posting question of i've tryed far... in constructor of outterpanel i've added componentlistener resize innerpanel:

jpanel outterpanel = this;  this.addcomponentlistener(new componentadapter() {     @override     public void componentresized(componentevent e) {         contentarea.setpreferredsize(new dimension(outterpanel.getpreferredsize().width, 500));     } }); 

the listener working, problem outterpanel.getpreferredsize().width, returning 0. reason, outterpanel.getpreferredsize().height return real height.

how can retrieve outterpanel width? , whats best path set innerpanel size?

override getpreferredsize() method of inner panel.

maybe like:

@override public dimension getpreferredsize() {     dimension parentsize = getparent().getsize();     int width = (parentsize.width / 50) * 50;     int height = (parentsize.height / 50) * 50;     return new dimension(width, height); }