java GridLayout布局里如何使设置按钮与边缘的间隙

java GridLayout布局里如何使设置按钮与边缘的间隙

import java.awt.GridLayout;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Test {

public static void main(String[] args) {
JFrame f=new JFrame();
//边缘空50
((JPanel)f.getContentPane()).setBorder(BorderFactory.createEmptyBorder(50,50,50,50));
//水平间隔120，垂直间隔80
f.getContentPane().setLayout(new GridLayout(3,3,120,80));
f.setSize(800,600);
for(int i=0; i<7; i++){
f.getContentPane().add(new JButton("bt "+String.valueOf(i+1)));
}
f.setVisible(true);
}
}