这个错误是怎么回事? 大家帮忙看看
Exception in thread "main" java.lang.NullPointerException
at JPaneltest.myColorPanel.<init>(myColorPanel.java:16)
at JPaneltest.mydrawapplication.<init>(mydrawapplication.java:10)
at JPaneltest.mydrawapplication.main(mydrawapplication.java:27)