java类中的静态全局变量使用注意事项

案例：

public class DemoTest {
    public static String lastDay = DateUtils.getDateTime4Format("yyyyMMddHHmmss");

public class DemoMain {
    public static void main(String[] args) throws Exception{
        System.out.println(DemoTest.lastDay);
        Thread.sleep(10000L);
        System.out.println(DemoTest.lastDay);
        String curDay = DateUtils.getDateTime4Format("yyyyMMddHHmmss");
        System.out.println(curDay);
    }
}

注意：静态全局变量，在程序启动时，只会被加载一次