Container.paint(Graphics g) 方法 -Java学习笔记(34)

本文介绍了一个简单的Java应用程序,该程序通过重写Frame子类的paint方法来绘制图形。演示了如何使用Graphics类绘制线条、填充矩形及显示字符串。
 在类Container及其子类(如:Frame,Panel)的对象需要重绘时,JVM会自动调用它的public void paint(Graphics g)方法。
//: PaintTest.java
import java.awt.*;
/**
 * Method Container.pain() Test.
 * Using paint() to draw some shapes.
 * 
@author nyzhl
*/

public class PaintTest {
    
public static void main (String[] args) {
        
new MyFrame();
    }
     
}

/**
 * Design window
*/

class MyFrame extends Frame {
    
public MyFrame() {
        setBounds(
200,200,200,200);
        setVisible(
true);
    }

    
public void paint(Graphics g) {
        Color c 
= g.getColor();
        g.setColor(Color.red);
        g.drawLine(
20,20,100,80);
        g.setColor(Color.blue);
        g.fill3DRect(
50,50,50,80,true);
        g.setColor(Color.yellow);
        g.drawString(
"PaintTest.java",50,150);
        g.setColor(c);
    }

}

///:~

效果:
[root@yfw ~]# cd /opt/openfire [root@yfw openfire]# # 查看完整的 openfire.log,从最近一次重启开始 [root@yfw openfire]# tail -n 200 /opt/openfire/logs/openfire.log | grep -A 20 -B 5 "Plugin 'restapi' was removed" at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:07:24.817 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:07:24.817 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:07:44.818 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:07:44.819 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:08:04.820 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:08:04.820 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:08:24.821 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:08:24.821 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:08:44.823 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:08:44.823 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:09:04.824 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:09:04.824 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:09:24.825 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:09:24.826 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:09:44.560 INFO [Thread-2]: org.jivesoftware.openfire.XMPPServer - Shutting down plugins ... 2025.10.03 04:09:44.560 INFO [Thread-2]: org.jivesoftware.openfire.container.PluginManager - Shutting down. Unloading all loaded plugins... 2025.10.03 04:09:44.562 INFO [Thread-2]: org.jivesoftware.openfire.XMPPServer - Shutting down 54 modules ... 2025.10.03 04:09:44.735 INFO [shutdown-thread-0]: org.jivesoftware.openfire.pubsub.DefaultPubSubPersistenceProvider - Flushing write cache to database 2025.10.03 04:09:44.738 INFO [shutdown-thread-0]: org.jivesoftware.openfire.OfflineMessageStore - Offline message cleaning - Stop old timer if started 2025.10.03 04:09:44.748 INFO [Thread-2]: org.jivesoftware.openfire.XMPPServer - Openfire stopped 2025.10.03 04:09:46.319 INFO [main]: org.jivesoftware.openfire.XMPPServer - Registering shutdown hook (standalone mode) 2025.10.03 04:09:46.861 INFO [main]: org.jivesoftware.util.cache.ConsistencyMonitor - Applying configuration for cache consistency check. Enabled: false 2025.10.03 04:09:46.874 INFO [main]: org.jivesoftware.util.cache.CacheFactory - Created cache [org.jivesoftware.util.cache.DefaultLocalCacheStrategy] for Routing Servers Cache 2025.10.03 04:09:46.875 INFO [main]: org.jivesoftware.util.cache.CacheFactory - Created cache [org.jivesoftware.util.cache.DefaultLocalCacheStrategy] for Routing Components Cache -- 2025.10.03 04:09:47.476 INFO [main]: org.jivesoftware.openfire.muc.spi.MultiUserChatServiceImpl - Rescheduling user idle task, recurring every PT15M 2025.10.03 04:09:47.480 INFO [main]: org.jivesoftware.openfire.muc.spi.MultiUserChatServiceImpl - 多用户聊天域:conference.localhost 2025.10.03 04:09:47.491 INFO [main]: org.jivesoftware.openfire.muc.spi.MultiUserChatServiceImpl - Rescheduling user idle task, recurring every PT15M 2025.10.03 04:09:47.492 INFO [main]: org.jivesoftware.openfire.muc.spi.MultiUserChatServiceImpl - 多用户聊天域:lobby.localhost 2025.10.03 04:09:47.508 INFO [main]: org.jivesoftware.openfire.XMPPServer - Openfire 4.9.2 [2025年10月3日 上午4:09:47] 2025.10.03 04:09:47.516 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:09:47.517 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:09:47.760 INFO [main]: org.jivesoftware.util.cache.CacheFactory - Created cache [org.jivesoftware.util.cache.DefaultLocalCacheStrategy] for LDAP UserDN 2025.10.03 04:09:48.181 INFO [main]: org.jivesoftware.openfire.net.SASLAuthentication - Support added for the 'ANONYMOUS' SASL mechanism. 2025.10.03 04:09:48.181 INFO [main]: org.jivesoftware.openfire.net.SASLAuthentication - Support added for the 'CRAM-MD5' SASL mechanism. 2025.10.03 04:09:48.181 INFO [main]: org.jivesoftware.openfire.net.SASLAuthentication - Support added for the 'DIGEST-MD5' SASL mechanism. 2025.10.03 04:09:48.181 INFO [main]: org.jivesoftware.openfire.net.SASLAuthentication - Support added for the 'EXTERNAL' SASL mechanism. 2025.10.03 04:09:48.182 INFO [main]: org.jivesoftware.openfire.net.SASLAuthentication - Support added for the 'GSSAPI' SASL mechanism. 2025.10.03 04:09:48.182 INFO [main]: org.jivesoftware.openfire.net.SASLAuthentication - Support added for the 'JIVE-SHAREDSECRET' SASL mechanism. 2025.10.03 04:09:48.182 INFO [main]: org.jivesoftware.openfire.net.SASLAuthentication - Support added for the 'PLAIN' SASL mechanism. 2025.10.03 04:09:48.182 INFO [main]: org.jivesoftware.openfire.net.SASLAuthentication - Support added for the 'SCRAM-SHA-1' SASL mechanism. 2025.10.03 04:09:48.220 INFO [main]: org.jivesoftware.util.cache.CacheFactory - Created cache [org.jivesoftware.util.cache.DefaultLocalCacheStrategy] for Remote Server Configurations 2025.10.03 04:10:07.552 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:10:07.552 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:10:27.554 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:10:27.555 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:10:47.556 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:10:47.556 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] 2025.10.03 04:11:07.557 INFO [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - Plugin 'restapi' was removed from the file system. 2025.10.03 04:11:07.558 ERROR [PluginMonitorTask-2]: org.jivesoftware.openfire.container.PluginMonitor - An unexpected exception occurred: java.lang.NullPointerException: null at org.jivesoftware.openfire.container.PluginManager.unloadPlugin(PluginManager.java:883) ~[xmppserver-4.9.2.jar:4.9.2] at org.jivesoftware.openfire.container.PluginMonitor$MonitorTask.run(PluginMonitor.java:305) [xmppserver-4.9.2.jar:4.9.2] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?] at java.lang.Thread.run(Thread.java:829) [?:?] [root@yfw openfire]#
最新发布
10-04
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