[英]Why does my PrintWriter throw exceptions when I try to write on it?
我有一個簡單的ChatClient,可以將數據發送到服務器。 為了使Chat Client發送數據,我制作了一個Socket,將PrintWriter制作到socket.getOutputStream(),然后執行writer.println(“”)。 由於某種原因,我得到了一個很大的例外。 我查看了與我類似的例外,很多人說要更新Java。 但是我的Mac上有最新版本。 是因為我有Leopard,還是我的劣質程序? 請看一下。
private void setUpNetworking() {
try {
**sock = new Socket("127.0.0.1", 65534);**
InputStreamReader streamReader = new InputStreamReader(sock.getInputStream());
reader = new BufferedReader(streamReader);
**writer = new PrintWriter(sock.getOutputStream());**
System.out.println("made connection... everything here works");
}
catch (IOException ex) {
ex.printStackTrace();
System.out.println("setup fail, but i didn't get this");
}
}
public class SendButtonListener implements ActionListener{
public void actionPerformed (ActionEvent ev){
try {
**writer.println(entertext.getText());**
**writer.flush();**
System.out.println("PROBLEM IS RIGHT HERE!!!");
}
catch (Exception ex) {
ex.printStackTrace();
System.out.println("i get a exception. HELP");
}
這是我的例外:
java.lang.NullPointerException
at SimpleChatClient$SendButtonListener.actionPerformed(SimpleChatClient.java:52)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1882)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2202)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:246)
at java.awt.Component.processMouseEvent(Component.java:5617)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3129)
at java.awt.Component.processEvent(Component.java:5382)
at java.awt.Container.processEvent(Container.java:2010)
at java.awt.Component.dispatchEventImpl(Component.java:4083)
at java.awt.Container.dispatchEventImpl(Container.java:2068)
at java.awt.Component.dispatchEvent(Component.java:3918)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4256)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3936)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3866)
at java.awt.Container.dispatchEventImpl(Container.java:2054)
at java.awt.Window.dispatchEventImpl(Window.java:1801)
at java.awt.Component.dispatchEvent(Component.java:3918)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:501)
at java.awt.EventQueue.access$000(EventQueue.java:80)
at java.awt.EventQueue$1.run(EventQueue.java:462)
at java.awt.EventQueue$1.run(EventQueue.java:461)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:84)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:95)
at java.awt.EventQueue$2.run(EventQueue.java:476)
at java.awt.EventQueue$2.run(EventQueue.java:475)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:84)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:473)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:190)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:176)
**at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)**
我不知道這是什么意思。 請幫忙。
從堆棧跟蹤和筆記中,聽起來就像當您調用
writer.println(entertext.getText());
在SendButtonListener
的actionPerformed
方法中, writer
enterText
為null。
哪個為空,如何從代碼中清除它是如何實現的,但是您應該能夠使用調試器或日志記錄來弄清楚。
調試方法如下:
println
以打印可能為null的所有內容 Chekc.SimpleChatClient的第52行,其中存在ir.null
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