Problem about SpringLayout in java 1.4.2

public static void main(String[] args) {
    // TODO code application logic here
        JFrame frame = new JFrame();

        SpringLayout layout = new SpringLayout();
        frame.getContentPane().setLayout(layout);
        TitledBorder border = null;
        border = BorderFactory.createTitledBorder("Group1");
        frame.setSize(620, 620);

 开发者_开发知识库       JPanel mainPanel = new JPanel();
        mainPanel.setBorder(border);
        //mainPanel.setPreferredSize( new Dimension(600,600));
        layout.putConstraint(SpringLayout.EAST, mainPanel, -15, SpringLayout.EAST, frame.getContentPane());
        layout.putConstraint(SpringLayout.WEST, mainPanel, 15, SpringLayout.WEST, frame.getContentPane());
        layout.putConstraint(SpringLayout.SOUTH, mainPanel, -15, SpringLayout.SOUTH, frame.getContentPane());
        layout.putConstraint(SpringLayout.NORTH, mainPanel, 15, SpringLayout.NORTH, frame.getContentPane());

        frame.getContentPane().add(mainPanel);
        frame.setVisible(true);
}

i am working on the effect with a panel auto-resize along with its parents while its parent resized in java 1.4.2. I used the SpringLayout to do this, but i found that if i define the SpringLayout.East and SpringLayout.South after the WEST and NORTH, the panel (mainPanel) will not posit at (15,15). It will do if EAST and NORTH are defined in front of WEST and SOUTH. Why is that?

As noted in this related question, the order of constraint specification may be important, particularly if the resulting layout is over-constrained. The order WEST, NORTH, EAST, SOUTH is an example that causes a reset, mentioned in the "Work Around Evaluation" section of a related bug report.