AWT布局有关问题

import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.JLabel;import java.awt.GridBagLayout;import java.awt.GridBagConstraints;import javax.swing.BorderFactory;import java.awt.Color;import java.awt.Dimension;public class Example {    public static void main(final String[] args) {        java.awt.EventQueue.invokeLater(new Runnable(){                @Override public void run(){                    JFrame frame = new JFrame("Example");                    JPanel container = new JPanel(new GridBagLayout());                    GridBagConstraints c = new GridBagConstraints();                    JPanel top = new JPanel();                    top.add(new JLabel("Top"));                    top.setBorder(BorderFactory.createLineBorder(Color.BLUE,3));                    c.gridx = 0; c.gridy = 0;                    c.weightx = 1;                    c.gridwidth = 2;                    c.fill = GridBagConstraints.BOTH;                    container.add(top,c);                    JPanel left = new JPanel();                    left.add(new JLabel("East"));                    left.setBorder(BorderFactory.createLineBorder(Color.BLACK,3));                    c.gridx = 0; c.gridy = 1;                    c.weightx = 0;                    c.gridwidth = 1;                //reset to the default                    c.weighty = 1.0;                    c.gridwidth = GridBagConstraints.RELATIVE;                    c.fill = GridBagConstraints.VERTICAL;                    container.add(left,c);                    JPanel center = new JPanel();                    center.add(new JLabel("Center"));                    center.setBorder(BorderFactory.createLineBorder(Color.GREEN,3));                    c.gridx = 1; c.gridy = 1;                    c.gridwidth = GridBagConstraints.REMAINDER;                    c.fill = GridBagConstraints.BOTH;                    container.add(center,c);                    frame.setContentPane(container);                    frame.setPreferredSize(new Dimension(600,400));                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);                    frame.pack();                    frame.setVisible(true);                }            });    }}
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Java code
        JPanel panel = new JPanel();        panel.setLayout(new BorderLayout());        panel.add(top, BorderLayout.NORTH);        panel.add(left, BorderLayout.WEST);        panel.add(right, BorderLayout.CENTER);