java Swing 窗口居中

Toolkit kit = Toolkit.getDefaultToolkit(); // 工具包  
Dimension screenSize=kit.getScreenSize(); // 获取屏幕的尺寸  
setMinimumSize(new Dimension(1300, 700));// 设置一个窗口大小值  
Dimension compSize = RoomFrm.this.getSize();  
System.out.println(compSize);  
        System.out.println(screenSize);
        if (compSize.height > screenSize.height) {
            compSize.height = screenSize.height;
        }
        if (compSize.width > screenSize.width) {
            compSize.width = screenSize.width;
        }
    //x0=(screenSize.width - compSize.width) / 2;
        //y0=(screenSize.height - compSize.height) / 2)
        setLocation((screenSize.width - compSize.width) / 2,
                (screenSize.height - compSize.height) / 2);