getAppletContext().showDocument(new url())错误java.lang.NullPointerException

Question

getAppletContext().showDocument(new url("http://www.sina.com.cn"))(url我只是举个例子)
new url(url),在我的程序中没有Exception

Answer 1

多种情况了，是个空指针错误，
getAppletContext()没初始化啊，new url("http://www.sina.com.cn")返回空啊，showDocument()方法内部处理没判空啊，谁知道是哪错了。

Answer 2

getAppletContext().showDocument(new url())
你里面的new url() 肯定是为空了

Answer 3

new url() 不是空 
我用URL linkurl=new URL("http://www.sina.com.cn")
 我打印  System.out.println(linkurl.toString())能得到 http://www.sina.com.cn
整個錯誤如下;
Exception occurred during event dispatching:
java.lang.NullPointerException
at java.applet.Applet.getAppletContext(Applet.java:141)
at test.PieViewS.update(PieStatisitc.java:188)
at sun.awt.RepaintArea.update(RepaintArea.java:337)
at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:200)
at java.awt.Component.dispatchEventImpl(Component.java:2663)
at java.awt.Container.dispatchEventImpl(Container.java:1213)
at java.awt.Component.dispatchEvent(Component.java:2497)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:339)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:131)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:98)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:85)