java - Unwanted border around JPanel -

I'm creating a form with a JPNL inside some buttons to control some graphics and things for some reason I should be 10 px less wide than JPNL and 30 px less than actual graphics which I want to put it in. What is the reason for this problem?

This code is:

  public square window {public sheep goat; Public ButtonPanel Button Panel; PaintPanel Pentale Public; Public jeffrey frame; Public window (Sheep sheep) {It. Mirror = sheep; Frame = new jefframe ("sheep simulation"); Frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE); //frame.setSize (width, height); Border Layout Frame Layout = New Border Layout (); JPN Background = New JPN (Frame Layouts); Background.setBorder (BorderFactory.createEmptyBorder (5, 5, 5, 5)); ButtonPanel = new buttonPanel (this); Background.add (Border Layout. South, Button Panel. Button Box); Pentpanel = New PaintPanel (this); PaintPanel.setPreferredSize (new dimension (320, 240)); Background.add (border layout.citter, paintpennel); . Add frame.getContentPane () (background); Frame.pack (); Frame.setResizable (wrong); Frame.setVisible (true); }} Public class PaintPanel JPanel {public window window; Public PaintPanel (Window Window) {this.window = window; } @ Override Public Love Paint Coment (Graphics G) {G. Setler (colored blue); G.fillRect (0, 0, 320, 240); }}  

Screenshots with the favorite sequence of 320 x 240:

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You can see that the 320 x 240 Fill JPNLL is fully, the limit of 10 px width and height of 30 px remains.

Screenshots with favorite seams of 310 x 210:

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Now it fits 320x 240 filling at all!

Any thoughts?