`Exception in thread "main" java.lang.NullPointerException at com.njupt.sms.ui.Login.<init>(Login.java:31) at Main.main(Main.java:18) `
Exception in thread "main" java.lang.NullPointerException at com.njupt.sms.ui.Login.<init>(Login.java:31) at Main.main(Main.java:18)