此栏用于向用户显示 URL 到 IP 转换的进度，基本上你输入一个网站 url 列表，它会将它们转换为 IP 地址，这一切都很好，但是在长列表中可能需要几秒钟这就是为什么我要添加进度条。
我之前使用过进度条来为用户提供已完成下载的百分比，但是在这种情况下，它似乎不喜欢我给它的值。例如，如果我打印它正确打印的值，
20
40
60
80
100
打印时
System.out.println(Progress.percentage);
但是，当我尝试为进度条设置新字符串或新值时，它会崩溃。
try {
Progress.main(null);
Progress.totalToDo = IPArray.size();
for (String URL : IPArray) {
URL url = new URL(URL);
InetAddress address = InetAddress.getByName(url.getHost());
String temp = address.toString();
String IP = temp.substring(temp.indexOf("/") + 1, temp.length());
URLArray.add(IP);
Progress.percentage = (URLArray.size() * 100) / Progress.totalToDo;
Progress.ipProgress.setString(Progress.percentage + "%");
Progress.ipProgress.setValue(Progress.percentage);
result += IP + System.getProperty("line.separator");
}
IPFrame.textAreaIP.setText(result);
GEOLookup.check(IPFrame.textAreaIP.getText());
}
如果您需要更多信息，请不要害怕询问，感谢您的帮助。
编辑：抱歉忘记发布它打印的错误，我知道错误是由
Progress.ipProgress.setString(Progress.percentage + "%");
Progress.ipProgress.setValue(Progress.percentage);
因为一旦删除，应用程序就会正常进行。打印的错误如下。
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at com.elvazar.ipgrabber.IPGrabber.convert(IPGrabber.java:86)
at com.elvazar.ipgrabber.IPFrame.jButton4ActionPerformed(IPFrame.java:335)
at com.elvazar.ipgrabber.IPFrame.access$700(IPFrame.java:23)
at com.elvazar.ipgrabber.IPFrame$8.actionPerformed(IPFrame.java:125)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)