我想在applet中显示随机编号，只要applet正在运行，但它没有显示。请指导代码是怎么回事
package javaapplication1;
import java.util.*;
import java.applet.Applet;
import java.awt.Graphics;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
public class set extends Applet implements Runnable {
private DateFormat formatter = null;
private Thread t = null;
public void init() {
int n = (int)(10.0 * Math.random()) + 1;
System.out.print(n);
t = new Thread(this);
}
public void start() {
t.start();
}
public void stop() {
t = null;
}
public void paint(Graphics g) {
Date now = Calendar.getInstance().getTime();
//
// Show the current time on the browser status bar
//
this.showStatus(formatter.format(now));
}
public void run() {
int delay = 1000;
try {
while (t == Thread.currentThread()) {
//
// Repaint the applet every on second
//
repaint();
Thread.sleep(delay);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
和它的浮动，有以下异常
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at javaapplication1.set.paint(set.java:39)
at sun.awt.RepaintArea.paintComponent(RepaintArea.java:248)
at sun.awt.RepaintArea.paint(RepaintArea.java:224)
at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:310)
at java.awt.Component.dispatchEventImpl(Component.java:4706)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at javaapplication1.set.paint(set.java:39)
at sun.awt.RepaintArea.paintComponent(RepaintArea.java:248)
at sun.awt.RepaintArea.paint(RepaintArea.java:224)
at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:310)
at java.awt.Component.dispatchEventImpl(Component.java:4706)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
4Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at javaapplication1.set.paint(set.java:39)
at java.awt.Container.update(Container.java:1801)
at sun.awt.RepaintArea.updateComponent(RepaintArea.java:239)
at sun.awt.RepaintArea.paint(RepaintArea.java:216)
at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:310)
at java.awt.Component.dispatchEventImpl(Component.java:4706)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at javaapplication1.set.paint(set.java:39)
at java.awt.Container.update(Container.java:1801)
at sun.awt.RepaintArea.updateComponent(RepaintArea.java:239)
at sun.awt.RepaintArea.paint(RepaintArea.java:216)
at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:310)
at java.awt.Component.dispatchEventImpl(Component.java:4706)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at javaapplication1.set.paint(set.java:39)
at java.awt.Container.update(Container.java:1801)
at sun.awt.RepaintArea.updateComponent(RepaintArea.java:239)
at sun.awt.RepaintArea.paint(RepaintArea.java:216)
at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:310)
at java.awt.Component.dispatchEventImpl(Component.java:4706)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at javaapplication1.set.paint(set.java:39)
at java.awt.Container.update(Container.java:1801)
at sun.awt.RepaintArea.updateComponent(RepaintArea.java:239)
at sun.awt.RepaintArea.paint(RepaintArea.java:216)
at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:310)
at java.awt.Component.dispatchEventImpl(Component.java:4706)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at javaapplication1.set.paint(set.java:39)
at java.awt.Container.update(Container.java:1801)
at sun.awt.RepaintArea.updateComponent(RepaintArea.java:239)
at sun.awt.RepaintArea.paint(RepaintArea.java:216)
at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:310)
at java.awt.Component.dispatchEventImpl(Component.java:4706)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
这应该不难。当您尝试在null上执行操作时，会发生NullPointerException。
在你的自己的代码中有一个NullPointerException(与库中的代码相反)。你所要做的就是去那一行，看看有什么可能是null。
this.showStatus(formatter.format(now));
formatter(最有可能)是null。这就是NullPointerException的原因。
我觉得stackoverflow让人变得无限懒惰
您希望如何显示它，您认为哪一部分代码将实现这一点?
此刻我可以看到你创建一个随机数，然后用这个号码调用System.out.println。这将把数字打印出来到控制台，但不会在applet中显示。
你需要在paint(Graphics g)方法中加入一些逻辑来显示这个数字——例如，调用g.d drawstring()。然而，根据您希望它如何看待您已经拥有的内容，您可能有多种输出文本的方式，因此不可能给出一个正确的或更具体的答案。
您应该再看一下applet教程，该教程介绍了如何控制输出，并可能根据该教程的结果返回更多特定的问题。