java.lang.NullPointerException
at com.sun.tools.javac.comp.Infer.getParameterizedSupers(Infer.java:625)
at com.sun.tools.javac.comp.Infer.access$200(Infer.java:64)
at com.sun.tools.javac.comp.Infer$IncorporationStep$7.apply(Infer.java:789)
at com.sun.tools.javac.comp.Infer.checkWithinBounds(Infer.java:552)
at com.sun.tools.javac.comp.Infer$GraphSolver.solve(Infer.java:1580)
at com.sun.tools.javac.comp.Infer$InferenceContext.solve(Infer.java:2202)
at com.sun.tools.javac.comp.Infer$InferenceContext.solve(Infer.java:2194)
at com.sun.tools.javac.comp.Infer$InferenceContext.solve(Infer.java:2209)
at com.sun.tools.javac.comp.Infer.instantiateMethod(Infer.java:186)
at com.sun.tools.javac.comp.Resolve.rawInstantiate(Resolve.java:567)
at com.sun.tools.javac.comp.Resolve.checkMethod(Resolve.java:604)
at com.sun.tools.javac.comp.Attr.checkMethod(Attr.java:3829)
at com.sun.tools.javac.comp.Attr.checkIdInternal(Attr.java:3616)
at com.sun.tools.javac.comp.Attr.checkMethodIdInternal(Attr.java:3527)
at com.sun.tools.javac.comp.Attr.checkMethodId(Attr.java:3500)
at com.sun.tools.javac.comp.Attr.checkId(Attr.java:3488)
at com.sun.tools.javac.comp.Attr.visitIdent(Attr.java:3233)
at com.sun.tools.javac.tree.JCTree$JCIdent.accept(JCTree.java:2011)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:576)
at com.sun.tools.javac.comp.Attr.visitApply(Attr.java:1825)
at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1465)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:576)
at com.sun.tools.javac.comp.Attr.attribExpr(Attr.java:618)
at com.sun.tools.javac.comp.Attr.visitVarDef(Attr.java:1075)
at com.sun.tools.javac.tree.JCTree$JCVariableDecl.accept(JCTree.java:852)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:576)
at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:645)
at com.sun.tools.javac.comp.Attr.attribStats(Attr.java:661)
at com.sun.tools.javac.comp.Attr.visitBlock(Attr.java:1124)
at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:909)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:576)
at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:645)
at com.sun.tools.javac.comp.Attr.visitMethodDef(Attr.java:1013)
at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:778)
at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:576)
at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:645)
at com.sun.tools.javac.comp.Attr.attribClassBody(Attr.java:4364)
at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:4272)
at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:4201)
at com.sun.tools.javac.comp.Attr.attrib(Attr.java:4176)
at com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1248)
at com.sun.tools.javac.main.JavaCompiler.compile2(JavaCompiler.java:901)
at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:860)
at com.sun.tools.javac.main.Main.compile(Main.java:523)
at com.sun.tools.javac.main.Main.compile(Main.java:381)
at com.sun.tools.javac.main.Main.compile(Main.java:370)
at com.sun.tools.javac.main.Main.compile(Main.java:361)
at com.sun.tools.javac.Main.compile(Main.java:56)
at com.sun.tools.javac.Main.main(Main.java:42)