如果您对加载属性文件时出现JavaNullPointerException和java载入错误感兴趣，那么这篇文章一定是您不可错过的。我们将详细讲解加载属性文件时出现JavaNullPointerExc
如果您对加载属性文件时出现Java NullPointerException和java载入错误感兴趣，那么这篇文章一定是您不可错过的。我们将详细讲解加载属性文件时出现Java NullPointerException的各种细节，并对java载入错误进行深入的分析，此外还有关于(java.lang.NullPointerException)数据库的链接时出的错、android – 获取截图时出现意外错误 – java.lang.nullpointerexception、Android----java.lang.NullPointerException:---java.lang.NullPointerException:、Exception in thread "main" java.lang.NullPointerException的实用技巧。
本文目录一览：- 加载属性文件时出现Java NullPointerException（java载入错误）
- (java.lang.NullPointerException)数据库的链接时出的错
- android – 获取截图时出现意外错误 – java.lang.nullpointerexception
- Android----java.lang.NullPointerException:---java.lang.NullPointerException:
- Exception in thread "main" java.lang.NullPointerException
加载属性文件时出现Java NullPointerException（java载入错误）
public class SupplierCalculatorApplet extends JApplet{...public void init(){ loadProperties(); ...}...private void loadProperties() { language = "en-us";//getParameter("Language"); prop = new Properties(); try { URL urlToProps = this.getClass().getResource("config/" + language + ".properties"); prop.load(urlToProps.openStream());//Exception Caught Here } catch (IOException e) { } }在上面指出的行中发现异常。无论语言是否是有效的属性文件，我都会在同一行上捕获相同的异常。
答案1
小编典典改成：
prop.load(this.getClass().getResourceAsStream("/config/" + language + ".properties"));
(java.lang.NullPointerException)数据库的链接时出的错
严重: Servlet.service() for servlet [jsp] in context with path [/2.26] threw exception [java.lang.NullPointerException] with root cause java.lang.NullPointerException at org.apache.jsp.insert2_jsp._jspService(insert2_jsp.java:98) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619)
我写的源码为：
Connection conn=null;
Statement stat=null;
try{
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/dbfk","root","liang");
stat = conn.createStatement();
String sql = "INSERT INTO fk(name,password,fktime) VALUES(''" +
name1+"'',''"+password1+ "'',''"+mDatetime+"'')";
stat.executeUpdate(sql);
}
catch(SQLException sqlException){
out.println(sqlException);
}
finally{
stat.close();
conn.close();
}
%>
<script type="text/javascript">
window.alert("注册成功!");
</script>
不知道报错的原因，网上搜了，也没找到办法，希望大家帮帮忙，谢谢了！！
android – 获取截图时出现意外错误 – java.lang.nullpointerexception
Unexpected Error while obtaining screenshot - java.lang.Nullpointerexception
我google了,并查看了不同的stackoverflow问题,但没有发现任何可以解决此问题.
我最近安装了Android Studio 2.0,这可能是我不知道的问题.
解决方法
如果你有getActivity().getwindow().addFlags(LayoutParams.FLAG_SECURE);设置(通常用于避免截图),它还会阻止您从Android Studio截取屏幕截图,在获取屏幕截图时生成相同的错误意外错误.
Android----java.lang.NullPointerException:---java.lang.NullPointerException:
2021-03-06 13:26:12.274 8544-8544/com.example.helloworld E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.helloworld,PID: 8544
java.lang.NullPointerException:: Unable to start activity ComponentInfo{com.example.helloworld/com.example.helloworld.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.CheckBox.setonCheckedchangelistener(android.widget.CompoundButton$OnCheckedchangelistener)' on a null object reference
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:3897)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4076)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2473)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:219)
at android.app.ActivityThread.main(ActivityThread.java:8349)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1055)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.CheckBox.setonCheckedchangelistener(android.widget.CompoundButton$OnCheckedchangelistener)' on a null object reference
at com.example.helloworld.MainActivity.setListener(MainActivity.java:161)
at com.example.helloworld.MainActivity.onCreate(MainActivity.java:138)
at android.app.Activity.performCreate(Activity.java:8085)
at android.app.Activity.performCreate(Activity.java:8073)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1320)
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:3870)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4076)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2473)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:219)
at android.app.ActivityThread.main(ActivityThread.java:8349)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1055)
2021-03-06 13:26:12.282 8544-8544/com.example.helloworld I/Process: Sending signal. PID: 8544 SIG: 9
检查一下xml文件定义的checkBox的id和在activity里获取的id是否一致
问题出在运行时找不到对应的checkBox
Process: com.example.helloworld,PID: 21319
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.helloworld/com.example.helloworld.MoreActivity}: java.lang.illegalaccessexception: java.lang.class<com.example.helloworld.MoreActivity> is not accessible from java.lang.class<android.app.AppComponentFactory>
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:3815)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4076)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2473)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:219)
at android.app.ActivityThread.main(ActivityThread.java:8349)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1055)
Caused by: java.lang.illegalaccessexception: java.lang.class<com.example.helloworld.MoreActivity> is not accessible from java.lang.class<android.app.AppComponentFactory>
at java.lang.class.newInstance(Native Method)
at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:95)
at androidx.core.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:41)
at android.app.Instrumentation.newActivity(Instrumentation.java:1264)
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:3800)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4076)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2473)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:219)
at android.app.ActivityThread.main(ActivityThread.java:8349)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1055)
这是在清单文件没有注册activity
所有的activity类都必须是public 的 不然清单文件找不到，所以就无法运行
java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference;
这和问题一是一样的，因为找不到对应的id
博主链接：
页面布局常用：
android:id 为控件指定相应的ID
android:text 指定控件的文本，置尽量使用strings.xml
android:grivity 指定控件的基本位置 ，比如举重，居右，
android:padding 指定控件的内边距，控件当中的内容
android:singleLine 如果设置为真的话，则将控件的内容在同一行当中显示
android:layout_above 将该空间的底部至于给定ID的空间之上
android:layout_below： 将该控件的顶部至于给定ID的控件之下
android:layout_toLeftOf： 将该控件的右边缘和给定ID的控件的左 边缘对其
android:layout_toRightOf 将该控件的左边缘和给定的ID的控件的右边缘对齐
android:layout_alignBaseLine 该控件的baseline和给定ID的控件的Baseline对齐
android:layout_alignBottom 将该控件的底部边缘与给定ID控件的底部边缘
android:layout_alignLeft 将该控件左边缘与给定ID控件的左边缘对齐
android:layout_alignRight 将该控件的右边缘与给定ID控件的右边缘对齐
android:layout_alignTop 将给定控件的顶部边缘与给定ID控件的顶部对齐
android:alignParentBottom 如果该值为true 则将该控件的底部和父控件的底部对齐
android:layout_alignParentLeft 如果该值为true则将该控件的左边与父控件的左边对齐
android:layout_alignParentRight 如果该值为true则将该控件的右边与父控件的右边对齐
android:layout_alignParentTop 将控件的顶部与父控件的顶部对齐
android:layout_centerHorizontal 如果值为真，该控件将被至于水平方向的中央
android:layout_centerInParent 将被至于父控件水平方向和垂直都居中
android:layout_centerVertical 将被至于垂直方向的中央
第一类:属性值为true或false
android:layout_centerHrizontal 水平居中
android:layout_centerVertical 垂直居中
android:layout_centerInparent 相对于父元素完全居中
android:layout_alignParentBottom 贴紧父元素的下边缘
android:layout_alignParentLeft 贴紧父元素的左边缘
android:layout_alignParentRight 贴紧父元素的右边缘
android:layout_alignParentTop 贴紧父元素的上边缘
android:layout_alignWithParentIfMissing 如果对应的兄弟元素找不到的话就以父元素做参照物
第二类：属性值必须为id的引用名“@id/id-name”
android:layout_below 在某元素的下方
android:layout_above 在某元素的的上方
android:layout_toLeftOf 在某元素的左边
android:layout_toRightOf 在某元素的右边
android:layout_alignTop 本元素的上边缘和某元素的的上边缘对齐
android:layout_alignLeft 本元素的左边缘和某元素的的左边缘对齐
android:layout_alignBottom 本元素的下边缘和某元素的的下边缘对齐
android:layout_alignRight 本元素的右边缘和某元素的的右边缘对齐
第三类：属性值为具体的像素值，如30dip，40px
android:layout_marginBottom 离父控件底边缘的距离
android:layout_marginLeft 离父控件左边缘的距离
android:layout_marginRight 离父控件右边缘的距离
android:layout_marginTop 离父控件上边缘的距离
EditText的android:hint
设置EditText为空时输入框内的提示信息。
android:gravity
android:gravity属性是对该view 内容的限定．比如一个button 上面的text. 你可以设置该text 在view的靠左，靠右等位置．以button为例，android:gravity=”right”则button上面的文字靠右
android:layout_gravity
android:layout_gravity是用来设置该view相对与起父view 的位置．比如一个button 在linearlayout里，你想把该button放在靠左、靠右等位置就可以通过该属性设置．以button为例，
android:layout_gravity=”right”则button靠右
android:layout_alignParentRight
使当前控件的右端和父控件的右端对齐。这里属性值只能为true或false，默认false。
padding和margin的区别：
所以padding是定义控件自己的内容和控件边缘之间的距离，padding有填充填料的意思，而margin是在说控件的四个边缘之外的距离，指的是和别的控件之间的距离，margin有边缘，页面留白的意思
原文链接：https://blog.csdn.net/qq_28296925/article/details/51115132
Exception in thread "main" java.lang.NullPointerException
hadoop-1.2.1+nutch-1.3
Exception in thread "main" java.lang.NullPointerException
at org.apache.nutch.fetcher.FetcherOutputFormat.checkOutputSpecs(FetcherOutputFormat.java:49)
at org.apache.hadoop.mapred.JobClient$2.run(JobClient.java:975)
at org.apache.hadoop.mapred.JobClient$2.run(JobClient.java:936)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:936)
at org.apache.hadoop.mapred.JobClient.submitJob(JobClient.java:910)
at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:1353)
at org.apache.nutch.fetcher.Fetcher.fetch(Fetcher.java:1107)
at org.apache.nutch.crawl.Crawl.run(Crawl.java:135)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
at org.apache.nutch.crawl.Crawl.main(Crawl.java:54)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.util.RunJar.main(RunJar.java:160)
nutch-site.xml
<configuration>
<property>
<name>http.agent.name</name>
<value>My Nutch Spider</value>
</property>
<property>
<name>http.robots.agents</name>
<value>My Nutch Spider,*</value>
</property>
</configuration>
我们今天的关于加载属性文件时出现Java NullPointerException和java载入错误的分享已经告一段落，感谢您的关注，如果您想了解更多关于(java.lang.NullPointerException)数据库的链接时出的错、android – 获取截图时出现意外错误 – java.lang.nullpointerexception、Android----java.lang.NullPointerException:---java.lang.NullPointerException:、Exception in thread "main" java.lang.NullPointerException的相关信息，请在本站查询。
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