我在分析项目时收到此错误：
java.lang.NullPointerException
at org.sonar.samples.java.checks.AvoidCoreClassRule.visitClass(AvoidCoreClassRule.java:51)
at org.sonar.java.model.declaration.ClassTreeImpl.accept(ClassTreeImpl.java:198)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.visitNewClass(BaseTreeVisitor.java:238)
at org.sonar.java.model.expression.NewClassTreeImpl.accept(NewClassTreeImpl.java:119)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.visitMemberSelectExpression(BaseTreeVisitor.java:228)
at org.sonar.java.model.expression.MemberSelectExpressionTreeImpl.accept(MemberSelectExpressionTreeImpl.java:115)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.visitMethodInvocation(BaseTreeVisitor.java:250)
at org.sonar.java.model.expression.MethodInvocationTreeImpl.accept(MethodInvocationTreeImpl.java:82)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.visitVariable(BaseTreeVisitor.java:292)
at org.sonar.java.model.declaration.VariableTreeImpl.accept(VariableTreeImpl.java:179)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:37)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.visitBlock(BaseTreeVisitor.java:85)
at org.sonar.java.model.statement.BlockTreeImpl.accept(BlockTreeImpl.java:77)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.visitTryStatement(BaseTreeVisitor.java:190)
at org.sonar.java.model.statement.TryStatementTreeImpl.accept(TryStatementTreeImpl.java:171)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:37)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.visitBlock(BaseTreeVisitor.java:85)
at org.sonar.java.model.statement.BlockTreeImpl.accept(BlockTreeImpl.java:77)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.visitMethod(BaseTreeVisitor.java:80)
at org.sonar.java.model.declaration.MethodTreeImpl.accept(MethodTreeImpl.java:218)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:37)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.visitClass(BaseTreeVisitor.java:69)
at org.sonar.samples.java.checks.AvoidCoreClassRule.visitClass(AvoidCoreClassRule.java:74)
at org.sonar.java.model.declaration.ClassTreeImpl.accept(ClassTreeImpl.java:198)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:37)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.visitCompilationUnit(BaseTreeVisitor.java:55)
at org.sonar.java.model.JavaTree$CompilationUnitTreeImpl.accept(JavaTree.java:143)
at org.sonar.plugins.java.api.tree.BaseTreeVisitor.scan(BaseTreeVisitor.java:43)
at org.sonar.samples.java.checks.AvoidCoreClassRule.scanFile(AvoidCoreClassRule.java:42)
at org.sonar.java.model.VisitorsBridge.visitFile(VisitorsBridge.java:127)
at org.sonar.java.ast.JavaAstScanner.simpleScan(JavaAstScanner.java:84)
at org.sonar.java.ast.JavaAstScanner.scan(JavaAstScanner.java:67)
at org.sonar.java.JavaSquid.scanSources(JavaSquid.java:135)
at org.sonar.java.JavaSquid.scan(JavaSquid.java:128)
at org.sonar.plugins.java.JavaSquidSensor.analyse(JavaSquidSensor.java:90)
at org.sonar.batch.phases.SensorsExecutor.executeSensor(SensorsExecutor.java:58)
at org.sonar.batch.phases.SensorsExecutor.execute(SensorsExecutor.java:50)
at org.sonar.batch.phases.PhaseExecutor.execute(PhaseExecutor.java:98)
at org.sonar.batch.scan.ModuleScanContainer.doAfterStart(ModuleScanContainer.java:185)
at org.sonar.core.platform.ComponentContainer.startComponents(ComponentContainer.java:132)
at org.sonar.core.platform.ComponentContainer.execute(ComponentContainer.java:117)
at org.sonar.batch.scan.ProjectScanContainer.scan(ProjectScanContainer.java:243)
at org.sonar.batch.scan.ProjectScanContainer.scanRecursively(ProjectScanContainer.java:238)
at org.sonar.batch.scan.ProjectScanContainer.doAfterStart(ProjectScanContainer.java:228)
at org.sonar.core.platform.ComponentContainer.startComponents(ComponentContainer.java:132)
at org.sonar.core.platform.ComponentContainer.execute(ComponentContainer.java:117)
at org.sonar.batch.task.ScanTask.execute(ScanTask.java:55)
at org.sonar.batch.task.TaskContainer.doAfterStart(TaskContainer.java:86)
at org.sonar.core.platform.ComponentContainer.startComponents(ComponentContainer.java:132)
at org.sonar.core.platform.ComponentContainer.execute(ComponentContainer.java:117)
at org.sonar.batch.bootstrap.GlobalContainer.executeTask(GlobalContainer.java:122)
at org.sonar.batch.bootstrapper.Batch.executeTask(Batch.java:119)
at org.sonar.batch.bootstrapper.Batch.execute(Batch.java:79)
at org.sonar.runner.batch.IsolatedLauncher.execute(IsolatedLauncher.java:48)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.sonar.runner.impl.BatchLauncher$1.delegateExecution(BatchLauncher.java:87)
at org.sonar.runner.impl.BatchLauncher$1.run(BatchLauncher.java:75)
at java.security.AccessController.doPrivileged(Native Method)
at org.sonar.runner.impl.BatchLauncher.doExecute(BatchLauncher.java:69)
at org.sonar.runner.impl.BatchLauncher.execute(BatchLauncher.java:50)
at org.sonar.runner.api.EmbeddedRunner.doExecute(EmbeddedRunner.java:102)
at org.sonar.runner.api.Runner.execute(Runner.java:100)
at org.sonarqube.gradle.SonarQubeTask.run(SonarQubeTask.java:53)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:75)
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.doExecute(AnnotationProcessingTaskFactory.java:226)
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:219)
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:208)
at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:585)
at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:568)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:80)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:61)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:46)
at org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:35)
at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:64)
at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:52)
at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52)
at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:53)
at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:203)
at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:185)
at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.processTask(AbstractTaskPlanExecutor.java:62)
at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.run(AbstractTaskPlanExecutor.java:50)
at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:25)
at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:110)
at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:37)
at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
at org.gradle.execution.DefaultBuildExecuter.access$000(DefaultBuildExecuter.java:23)
at org.gradle.execution.DefaultBuildExecuter$1.proceed(DefaultBuildExecuter.java:43)
at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:30)
at org.gradle.initialization.DefaultGradleLauncher$4.run(DefaultGradleLauncher.java:155)
at org.gradle.internal.Factories$1.create(Factories.java:22)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:52)
at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:152)
at org.gradle.initialization.DefaultGradleLauncher.access$200(DefaultGradleLauncher.java:33)
at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:100)
at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:94)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:62)
at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:94)
at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:83)
at org.gradle.launcher.exec.InProcessBuildActionExecuter$DefaultBuildController.run(InProcessBuildActionExecuter.java:94)
at org.gradle.tooling.internal.provider.ExecuteBuildActionRunner.run(ExecuteBuildActionRunner.java:28)
at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:43)
at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:28)
at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:77)
at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:47)
at org.gradle.launcher.exec.DaemonUsageSuggestingBuildActionExecuter.execute(DaemonUsageSuggestingBuildActionExecuter.java:51)
at org.gradle.launcher.exec.DaemonUsageSuggestingBuildActionExecuter.execute(DaemonUsageSuggestingBuildActionExecuter.java:28)
at org.gradle.launcher.cli.RunBuildAction.run(RunBuildAction.java:43)
at org.gradle.internal.Actions$RunnableActionAdapter.execute(Actions.java:170)
at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:237)
at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:210)
at org.gradle.launcher.cli.JavaRuntimeValidationAction.execute(JavaRuntimeValidationAction.java:35)
at org.gradle.launcher.cli.JavaRuntimeValidationAction.execute(JavaRuntimeValidationAction.java:24)
at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:206)
at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:169)
at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:33)
at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:22)
at org.gradle.launcher.Main.doAction(Main.java:33)
at org.gradle.launcher.bootstrap.EntryPoint.run(EntryPoint.java:45)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.gradle.launcher.bootstrap.ProcessBootstrap.runNoExit(ProcessBootstrap.java:54)
at org.gradle.launcher.bootstrap.ProcessBootstrap.run(ProcessBootstrap.java:35)
at org.gradle.launcher.GradleMain.main(GradleMain.java:23)
声纳正确分析所有类，但在没有其他类的两个类之间会出现此错误。调用类树的 simpleName（） 方法时会发生此错误。
@Override
public void visitClass(ClassTree tree) {
String className = "No change";
try {
className = tree.simpleName().name();
} catch (Exception e){
e.printStackTrace();
}
//...
}
如果您查看 API，simpleName() 方法会用 @Nullable 进行注释，因此您最终可能会得到此方法返回的 null 值。
为什么会这样？因为类树也用于匿名类（new mypackage.MyClass() { ... }构造）的主体，在这种情况下NewClassTree，classTree没有名称（所以它是空的）。（另一种情况也适用于枚举常量主体）。