A DESCRIPTION OF THE PROBLEM :
NPE occurs when internal class extends a generic parameter.
Stacktrace:
java.lang.NullPointerException
at com.sun.tools.javac.code.Types.getBounds(Types.java:2538)
at com.sun.tools.javac.comp.Check.checkNonCyclic1(Check.java:2195)
at com.sun.tools.javac.comp.Check.checkNonCyclic1(Check.java:2196)
at com.sun.tools.javac.comp.Check.checkNonCyclic(Check.java:2181)
at com.sun.tools.javac.comp.Attr.attribTypeVariables(Attr.java:713)
at com.sun.tools.javac.comp.MemberEnter.complete(MemberEnter.java:1117)
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.comp.Resolve.isAccessible(Resolve.java:369)
at com.sun.tools.javac.comp.Resolve.isAccessible(Resolve.java:365)
at com.sun.tools.javac.comp.Resolve.findImmediateMemberType(Resolve.java:1923)
at com.sun.tools.javac.comp.Resolve.findMemberType(Resolve.java:1978)
at com.sun.tools.javac.comp.Resolve.findIdentInType(Resolve.java:2162)
at com.sun.tools.javac.comp.Attr.selectSym(Attr.java:3388)
at com.sun.tools.javac.comp.Attr.visitSelect(Attr.java:3254)
at com.sun.tools.javac.tree.JCTree$JCFieldAccess.accept(JCTree.java:1897)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:566)
at com.sun.tools.javac.comp.Attr.attribType(Attr.java:628)
at com.sun.tools.javac.comp.Attr.attribType(Attr.java:621)
at com.sun.tools.javac.comp.Attr.visitTypeApply(Attr.java:3887)
at com.sun.tools.javac.tree.JCTree$JCTypeApply.accept(JCTree.java:2135)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:566)
at com.sun.tools.javac.comp.Attr.attribType(Attr.java:628)
at com.sun.tools.javac.comp.Attr.attribType(Attr.java:621)
at com.sun.tools.javac.comp.Attr.attribAnyTypes(Attr.java:677)
at com.sun.tools.javac.comp.Attr.attribTypes(Attr.java:685)
at com.sun.tools.javac.comp.Attr.visitTypeApply(Attr.java:3890)
at com.sun.tools.javac.tree.JCTree$JCTypeApply.accept(JCTree.java:2135)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:566)
at com.sun.tools.javac.comp.Attr.attribType(Attr.java:628)
at com.sun.tools.javac.comp.Attr.attribType(Attr.java:621)
at com.sun.tools.javac.comp.Attr.attribBase(Attr.java:776)
at com.sun.tools.javac.comp.MemberEnter.complete(MemberEnter.java:1057)
at com.sun.tools.javac.code.Symbol.complete(Symbol.java:574)
at com.sun.tools.javac.code.Symbol$ClassSymbol.complete(Symbol.java:1037)
at com.sun.tools.javac.comp.Enter.complete(Enter.java:493)
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)
FREQUENCY : always