Execution failed for task ':core:compileJava': org.gradle.api.internal.tasks.compile.CompilationFailedException: Compilation failed; see the compiler error output for details. at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute(JdkJavaCompiler.java:58) at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute(JdkJavaCompiler.java:41) at org.gradle.api.internal.tasks.compile.daemon.AbstractDaemonCompiler$CompilerWorkAction.execute(AbstractDaemonCompiler.java:135) at org.gradle.workers.internal.DefaultWorkerServer.execute(DefaultWorkerServer.java:63) at org.gradle.workers.internal.AbstractClassLoaderWorker$1.create(AbstractClassLoaderWorker.java:49) at org.gradle.workers.internal.AbstractClassLoaderWorker$1.create(AbstractClassLoaderWorker.java:43) at org.gradle.internal.classloader.ClassLoaderUtils.executeInClassloader(ClassLoaderUtils.java:100) at org.gradle.workers.internal.AbstractClassLoaderWorker.executeInClassLoader(AbstractClassLoaderWorker.java:43) at org.gradle.workers.internal.FlatClassLoaderWorker.run(FlatClassLoaderWorker.java:32) at org.gradle.workers.internal.FlatClassLoaderWorker.run(FlatClassLoaderWorker.java:22) at org.gradle.workers.internal.WorkerDaemonServer.run(WorkerDaemonServer.java:87) at org.gradle.workers.internal.WorkerDaemonServer.run(WorkerDaemonServer.java:56) at org.gradle.process.internal.worker.request.WorkerAction$1.call(WorkerAction.java:138) at org.gradle.process.internal.worker.child.WorkerLogEventListener.withWorkerLoggingProtocol(WorkerLogEventListener.java:41) at org.gradle.process.internal.worker.request.WorkerAction.run(WorkerAction.java:135) at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36) at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24) at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:182) at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:164) at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:414) at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64) at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:49) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at java.base/java.lang.Thread.run(Thread.java:829)

Execution failed for task ':core:compileJava'. > Compilation failed; see the compiler error output for details.

[Task :core:compileJava] [return.type.incompatible] incompatible types in return. if ( string == null) return null; ^ type of expression: null (NullType)