java中JTable如何用代码设置不随窗口变化而变化

    在学习JTable时发现我的表格会随着JAVA窗口的变化而变化，想知道如何不让它
变化，也就是说如何让它固定化？

代码如下：

package com.view;

import java.awt.Color;

import javax.swing.*;

public class NewFrame extends JFrame
{
private String[] columnNames=
{
"Country","Capital","Population in Millions","Democracy"
};

private Object[][] data=
    {
        {"USA","Washington DC",280,true},
        {"Canada","Ottawa",32,true},
        {"China","Beijing",1000,true},
        {"Japan","Tokyo",50,true},
    };

private JTable jTable1=new JTable(data,columnNames);

public NewFrame()
{
    jTable1.setBackground(Color.RED);
    add(new JScrollPane(jTable1));
}

public static void main(String[]args)
{
    NewFrame frame=new NewFrame();
    frame.setSize(600, 400);
    frame.setLocationRelativeTo(null);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
}

}

frame.setLayout(null);//frame不使用布局管理器
jTable1.setPreferredSize(new Dimension(400, 400));//设置table的固定大小