java怎么将组件居中

import java.awt.Toolkit;
import javax.swing.JFrame;
@SuppressWarnings("serial")
public class AppWindows extends JFrame {
    // 得到显示器屏幕的宽高
    public int width = Toolkit.getDefaultToolkit().getScreenSize().width;
    public int height = Toolkit.getDefaultToolkit().getScreenSize().height;
    // 定义窗体的宽高
    public int windowsWedth = 600;
    public int windowsHeight = 600;
    public AppWindows() {
        // 设置窗体可见
        this.setVisible(true);
        // 设置窗体位置和大小
        this.setBounds((width - windowsWedth) / 2,
                (height - windowsHeight) / 2, windowsWedth, windowsHeight);
    }
    
    public static void main(String[] args) {
        new AppWindows();
    }
}

JPanel jPanel1=new Jpanel();//new一个Jpanel
BorderLayout bb=new BorderLayout();  //边界布局，设置控件垂直居中
jPanel1.setLayout(bb);
jLabel1.setHorizontalAlignment(SwingConstants.CENTER);  //设置控件左右居中