What's wrong ---Exception in thread "main" java.lang.NullPointerException
Exception in thread "main" java.lang.NullPointerException
at java.awt.Container.addImpl(Container.java:341)
at java.awt.Container.add(Container.java:267)
at Frame1.<init>(Frame1.java:59)
at Frame1.main(Frame1.java:69)
请问这是什么错?