java 随意控制控件的位置

package chat1;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class chat1{

    public chat1(){

        JFrame jf = new JFrame();

        jf.setLayout(null);

        jf.setSize(280,560);

        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JButton logn = new JButton("logn");

        JButton out = new JButton("out");

        logn.setBounds(170,480,80,30);    //  参数分别为坐标，控件的规格

        out.setBounds(15,480,80,30);

        jf.add(logn);

        jf.add(out);

        jf.setVisible(true);

    }

    public static void main(String[] args){

        chat1 frame = new chat1();

    }

}