com.sun.tools.javac.util.FatalError: Fatal Error: Unable to find method append
   at com.sun.tools.javac.comp.Resolve.resolveInternalMethod(Resolve.java:1382)
   at com.sun.tools.javac.jvm.Gen.getStringBufferAppend(Gen.java:2016)
   at com.sun.tools.javac.jvm.Gen.appendString(Gen.java:2010)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2041)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2036)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2035)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2035)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2035)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2035)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2035)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2035)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2035)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2035)
   at com.sun.tools.javac.jvm.Gen.visitBinary(Gen.java:1956)
   at com.sun.tools.javac.tree.JCTree$JCBinary.accept(JCTree.java:1552)
   at com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:839)
   at com.sun.tools.javac.jvm.Gen.visitVarDef(Gen.java:1020)
   at com.sun.tools.javac.tree.JCTree$JCVariableDecl.accept(JCTree.java:717)
   at com.sun.tools.javac.jvm.Gen.genDef(Gen.java:686)
   at com.sun.tools.javac.jvm.Gen.genStat(Gen.java:721)
   at com.sun.tools.javac.jvm.Gen.genStat(Gen.java:707)
   at com.sun.tools.javac.jvm.Gen.genStats(Gen.java:758)
   at com.sun.tools.javac.jvm.Gen.visitBlock(Gen.java:1033)
   at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:773)
   at com.sun.tools.javac.jvm.Gen.genDef(Gen.java:686)
   at com.sun.tools.javac.jvm.Gen.genStat(Gen.java:721)
   at com.sun.tools.javac.jvm.Gen.genMethod(Gen.java:914)
   at com.sun.tools.javac.jvm.Gen.visitMethodDef(Gen.java:887)
   at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:660)
   at com.sun.tools.javac.jvm.Gen.genDef(Gen.java:686)
   at com.sun.tools.javac.jvm.Gen.genClass(Gen.java:2272)
   at com.sun.tools.javac.main.JavaCompiler.genCode(JavaCompiler.java:737)
   at com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1492)
   at com.sun.tools.javac.api.JavacTaskImpl$3.process(JavacTaskImpl.java:542)
   at com.sun.tools.javac.api.JavacTaskImpl$Filter.run(JavacTaskImpl.java:630)
   at com.sun.tools.javac.api.JavacTaskImpl.generate(JavacTaskImpl.java:545)
   at org.netbeans.modules.java.source.indexing.MultiPassCompileWorker.compile(MultiPassCompileWorker.java:276)
   at org.netbeans.modules.java.source.indexing.JavaCustomIndexer$1.run(JavaCustomIndexer.java:208)
   at org.netbeans.modules.java.source.indexing.JavaCustomIndexer$1.run(JavaCustomIndexer.java:174)
   at org.netbeans.modules.java.source.usages.ClassIndexManager.prepareWriteLock(ClassIndexManager.java:117)
   at org.netbeans.modules.java.source.indexing.JavaCustomIndexer.index(JavaCustomIndexer.java:174)
   at org.netbeans.modules.parsing.spi.indexing.Indexable$MyAccessor$2.run(Indexable.java:175)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater.runIndexer(RepositoryUpdater.java:240)
   at org.netbeans.modules.parsing.spi.indexing.Indexable$MyAccessor.index(Indexable.java:173)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.doIndex(RepositoryUpdater.java:1680)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.access$1200(RepositoryUpdater.java:1437)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.run(RepositoryUpdater.java:1606)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.run(RepositoryUpdater.java:1604)
   at org.netbeans.modules.parsing.impl.indexing.errors.TaskCache.refreshTransaction(TaskCache.java:454)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.index(RepositoryUpdater.java:1604)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$AbstractRootsWork.scanSource(RepositoryUpdater.java:3226)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$AbstractRootsWork.scanSources(RepositoryUpdater.java:3126)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$RootsWork.getDone(RepositoryUpdater.java:2875)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.doTheWork(RepositoryUpdater.java:2015)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task._run(RepositoryUpdater.java:3614)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task.run(RepositoryUpdater.java:3554)
   at org.netbeans.modules.parsing.impl.TaskProcessor$CompilationJob.run(TaskProcessor.java:587)
   at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
   at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
   at java.util.concurrent.FutureTask.run(FutureTask.java:138)
   at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
   at java.lang.Thread.run(Thread.java:619)