java.lang.NullPointerException
        at com.sun.tools.javac.comp.MemberEnter.baseEnv(MemberEnter.java:1388)
        at com.sun.tools.javac.comp.MemberEnter.complete(MemberEnter.java:1046)
        at com.sun.tools.javac.code.Symbol.complete(Symbol.java:574)
        at com.sun.tools.javac.code.Symbol$ClassSymbol.complete(Symbol.java:1037)
        at com.sun.tools.javac.code.Symbol$ClassSymbol.flags(Symbol.java:973)
        at com.sun.tools.javac.code.Symbol$ClassSymbol.getKind(Symbol.java:1101)
        at com.sun.tools.javac.code.Kinds.kindName(Kinds.java:162)
        at com.sun.tools.javac.comp.Check.duplicateError(Check.java:329)
        at com.sun.tools.javac.comp.Check.checkUnique(Check.java:3380)
        at com.sun.tools.javac.comp.Enter.visitTypeParameter(Enter.java:454)
        at com.sun.tools.javac.tree.JCTree$JCTypeParameter.accept(JCTree.java:2224)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:258)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:272)
        at com.sun.tools.javac.comp.Enter.visitClassDef(Enter.java:418)
        at com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:693)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:258)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:272)
        at com.sun.tools.javac.comp.Enter.visitClassDef(Enter.java:426)
        at com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:693)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:258)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:272)
        at com.sun.tools.javac.comp.Enter.visitTopLevel(Enter.java:334)
        at com.sun.tools.javac.tree.JCTree$JCCompilationUnit.accept(JCTree.java:518)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:258)
        at com.sun.tools.javac.comp.Enter.classEnter(Enter.java:272)
        at com.sun.tools.javac.comp.Enter.complete(Enter.java:486)
        at com.sun.tools.javac.comp.Enter.main(Enter.java:471)
        at com.sun.tools.javac.main.JavaCompiler.enterTrees(JavaCompiler.java:982)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:857)
        at com.sun.tools.javac.main.Main.compile(Main.java:523)
        at com.sun.tools.javac.api.JavacTaskImpl.doCall(JavacTaskImpl.java:129)
        at com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:138)
        at org.codehaus.plexus.compiler.javac.JavaxToolsCompiler.compileInProcess(JavaxToolsCompiler.java:126)
        at org.codehaus.plexus.compiler.javac.JavacCompiler.performCompile(JavacCompiler.java:174)
        at org.apache.maven.plugin.compiler.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:1075)
        at org.apache.maven.plugin.compiler.CompilerMojo.execute(CompilerMojo.java:168)
        at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
        at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
        at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
        at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
        at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
        at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
        at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
        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.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
        at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
        at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)