CODEWITHSUNDEEP
javaandroidgenerics
Mukul
Mukul

Reputation: 141

How to use multiple bounds in java generics in this case

I am trying to create a constructor for something like this.

public <T extends AppCompatActivity & DialogInterface.OnDismissListener> GooglePlayUtils(T activity) {
    this.activity = activity;
}

Android studio doesn't give any complains about this, but build fails on CompileDebugJava

However if remove the second bound, compilation works fine. Am I doing it wrong or is there some other factor involved that I am missing?

Edit After adding the type parameter to class itself rather than constructor solved the issue for me. But am still keeping the question open so someone can give the explanation why so?

Edit 2 Added the type parameter to class instead of constructor

public abstract class GooglePlayUtils<T extends AppCompatActivity & DialogInterface.OnDismissListener> {

private T activity;

public GooglePlayUtils(T activity) {
    this.activity = activity;
}

Error

java.lang.AssertionError: at com.sun.tools.javac.util.Assert.error(Assert.java:133) at com.sun.tools.javac.util.Assert.check(Assert.java:86) at com.sun.tools.javac.comp.Attr.attribBounds(Attr.java:561) at com.sun.tools.javac.comp.Attr.visitMethodDef(Attr.java:723) at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:669) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:431) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:418) at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:480) at com.sun.tools.javac.comp.Attr.attribClassBody(Attr.java:3250) at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:3173) at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:3109) at com.sun.tools.javac.comp.Attr.visitClassDef(Attr.java:708) at com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:591) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:431) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:418) at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:480) at com.sun.tools.javac.comp.Attr.visitNewClass(Attr.java:1790) at com.sun.tools.javac.tree.JCTree$JCNewClass.accept(JCTree.java:1372) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:431) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:418) at com.sun.tools.javac.comp.Attr.attribExpr(Attr.java:449) at com.sun.tools.javac.comp.Attr.visitAssign(Attr.java:1993) at com.sun.tools.javac.tree.JCTree$JCAssign.accept(JCTree.java:1466) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:431) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:418) at com.sun.tools.javac.comp.Attr.attribExpr(Attr.java:460) at com.sun.tools.javac.comp.Attr.visitExec(Attr.java:1294) at com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1167) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:431) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:418) at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:480) at com.sun.tools.javac.comp.Attr.attribStats(Attr.java:496) at com.sun.tools.javac.comp.Attr.visitBlock(Attr.java:918) at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:781) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:431) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:418) at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:480) at com.sun.tools.javac.comp.Attr.visitMethodDef(Attr.java:836) at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:669) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:431) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:418) at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:480) at com.sun.tools.javac.comp.Attr.attribClassBody(Attr.java:3250) at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:3173) at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:3109) at com.sun.tools.javac.comp.Attr.attrib(Attr.java:3083) at com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1184) at com.sun.tools.javac.main.JavaCompiler.compile2(JavaCompiler.java:870) at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:829) at com.sun.tools.javac.main.Main.compile(Main.java:439) at com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:132) at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute(JdkJavaCompiler.java:45) at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute(JdkJavaCompiler.java:33) at org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler.delegateAndHandleErrors(NormalizingJavaCompiler.java:101) at org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler.execute(NormalizingJavaCompiler.java:50) at org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler.execute(NormalizingJavaCompiler.java:36) at org.gradle.api.internal.tasks.compile.CleaningJavaCompilerSupport.execute(CleaningJavaCompilerSupport.java:34) at org.gradle.api.internal.tasks.compile.CleaningJavaCompilerSupport.execute(CleaningJavaCompilerSupport.java:25) at org.gradle.api.tasks.compile.JavaCompile.performCompilation(JavaCompile.java:157) at org.gradle.api.tasks.compile.JavaCompile.compile(JavaCompile.java:137) at org.gradle.api.tasks.compile.JavaCompile.compile(JavaCompile.java:91) at sun.reflect.GeneratedMethodAccessor1481.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:75) at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$IncrementalTaskAction.doExecute(AnnotationProcessingTaskFactory.java:243) at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:219) at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$IncrementalTaskAction.execute(AnnotationProcessingTaskFactory.java:230) at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:208) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:80) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:61) at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:46) at org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:35) at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:64) at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58) at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:42) at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52) at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:53) at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43) at org.gradle.api.internal.AbstractTask.executeWithoutThrowingTaskFailure(AbstractTask.java:310) at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.executeTask(AbstractTaskPlanExecutor.java:79) at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.processTask(AbstractTaskPlanExecutor.java:63) at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.run(AbstractTaskPlanExecutor.java:51) at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:23) at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:88) at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:37) at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:62) at org.gradle.execution.DefaultBuildExecuter.access$200(DefaultBuildExecuter.java:23) at org.gradle.execution.DefaultBuildExecuter$2.proceed(DefaultBuildExecuter.java:68) at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32) at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:62) at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:55) at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:149) at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:106) at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:86) at org.gradle.launcher.exec.InProcessBuildActionExecuter$DefaultBuildController.run(InProcessBuildActionExecuter.java:90) at org.gradle.tooling.internal.provider.runner.BuildModelActionRunner.run(BuildModelActionRunner.java:54) at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35) at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:41) at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:28) at org.gradle.launcher.daemon.server.exec.ExecuteBuild.doBuild(ExecuteBuild.java:49) at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36) at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120) at org.gradle.launcher.daemon.server.exec.WatchForDisconnection.execute(WatchForDisconnection.java:37) at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120) at org.gradle.launcher.daemon.server.exec.ResetDeprecationLogger.execute(ResetDeprecationLogger.java:26) at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120) at org.gradle.launcher.daemon.server.exec.RequestStopIfSingleUsedDaemon.execute(RequestStopIfSingleUsedDaemon.java:34) at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120) at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:74) at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:72) at org.gradle.util.Swapper.swap(Swapper.java:38) at org.gradle.launcher.daemon.server.exec.ForwardClientInput.execute(ForwardClientInput.java:72) at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120) at org.gradle.launcher.daemon.server.health.DaemonHealthTracker.execute(DaemonHealthTracker.java:47) at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120) at org.gradle.launcher.daemon.server.exec.LogToClient.doBuild(LogToClient.java:66) at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36) at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120) at org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment.doBuild(EstablishBuildEnvironment.java:71) at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36) at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120) at org.gradle.launcher.daemon.server.health.HintGCAfterBuild.execute(HintGCAfterBuild.java:41) at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120) at org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy$1.run(StartBuildOrRespondWithBusy.java:50) at org.gradle.launcher.daemon.server.DaemonStateCoordinator$1.run(DaemonStateCoordinator.java:246) at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:54) at org.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:40) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745)

Upvotes: 1

Views: 148

Answers (1)

Lorne Laliberte
Lorne Laliberte

Reputation: 6311

Were you trying to create a generic class, or a concrete class whose constructor takes generic arguments?

If you were trying to create a generic class, that can be instantiated for objects that extend AppCompatActivity & DialogInterface.OnDismissListener, you need to make the class generic (as in your edit). In a generic class, the class type parameters don't need to be repeated in the constructor definition, they are assumed by the compiler implicitly.

If you were trying to create a class of some concrete or generic type whose constructor can accept objects that extend AppCompatActivity & DialogInterface.OnDismissListener, you need a way to explicitly cast that parameter to whatever type this.activity is defined as. The only way to assign your generic activity parameter to this.activity without casting is if they are the same type after type erasure.

While it is possible to create a constructor whose arguments are generic, you cannot assign a generic argument to one of a different type (after type erasure) without casting.

Upvotes: 0

Related Questions