com.sun.tools.javac.util.FatalError: Fatal Error: Unable to find method append
   at com.sun.tools.javac.comp.Resolve.resolveInternalMethod(Resolve.java:1546)
   at com.sun.tools.javac.jvm.Gen.getStringBufferAppend(Gen.java:1986)
   at com.sun.tools.javac.jvm.Gen.appendString(Gen.java:1980)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2011)
   at com.sun.tools.javac.jvm.Gen.appendStrings(Gen.java:2006)
   at com.sun.tools.javac.jvm.Gen.visitBinary(Gen.java:1926)
   at com.sun.tools.javac.tree.JCTree$JCBinary.accept(JCTree.java:1570)
   at com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:840)
   at com.sun.tools.javac.jvm.Gen.visitParens(Gen.java:1784)
   at com.sun.tools.javac.tree.JCTree$JCParens.accept(JCTree.java:1446)
   at com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:840)
   at com.sun.tools.javac.jvm.Gen.genArgs(Gen.java:859)
   at com.sun.tools.javac.jvm.Gen.visitApply(Gen.java:1693)
   at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1326)
   at com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:840)
   at com.sun.tools.javac.jvm.Gen.visitReturn(Gen.java:1662)
   at com.sun.tools.javac.tree.JCTree$JCReturn.accept(JCTree.java:1245)
   at com.sun.tools.javac.jvm.Gen.genDef(Gen.java:687)
   at com.sun.tools.javac.jvm.Gen.genStat(Gen.java:722)
   at com.sun.tools.javac.jvm.Gen.genStat(Gen.java:708)
   at com.sun.tools.javac.jvm.Gen.genStats(Gen.java:759)
   at com.sun.tools.javac.jvm.Gen.visitBlock(Gen.java:1034)
   at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:786)
   at com.sun.tools.javac.jvm.Gen.genDef(Gen.java:687)
   at com.sun.tools.javac.jvm.Gen.genStat(Gen.java:722)
   at com.sun.tools.javac.jvm.Gen.genMethod(Gen.java:915)
   at com.sun.tools.javac.jvm.Gen.visitMethodDef(Gen.java:888)
   at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:674)
   at com.sun.tools.javac.jvm.Gen.genDef(Gen.java:687)
   at com.sun.tools.javac.jvm.Gen.genClass(Gen.java:2235)
   at com.sun.tools.javac.main.JavaCompiler.genCode(JavaCompiler.java:736)
   at com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1520)
   at com.sun.tools.javac.api.JavacTaskImpl$3.process(JavacTaskImpl.java:543)
   at com.sun.tools.javac.api.JavacTaskImpl$Filter.run(JavacTaskImpl.java:631)
   at com.sun.tools.javac.api.JavacTaskImpl.generate(JavacTaskImpl.java:546)
   at org.netbeans.modules.java.source.indexing.MultiPassCompileWorker.compile(MultiPassCompileWorker.java:280)
   at org.netbeans.modules.java.source.indexing.JavaCustomIndexer$1.run(JavaCustomIndexer.java:199)
   at org.netbeans.modules.java.source.indexing.JavaCustomIndexer$1.run(JavaCustomIndexer.java:161)
   at org.netbeans.modules.java.source.usages.ClassIndexManager.prepareWriteLock(ClassIndexManager.java:120)
   at org.netbeans.modules.java.source.indexing.JavaCustomIndexer.index(JavaCustomIndexer.java:161)
   at org.netbeans.modules.parsing.spi.indexing.Indexable$MyAccessor$2.run(Indexable.java:153)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater.runIndexer(RepositoryUpdater.java:256)
   at org.netbeans.modules.parsing.spi.indexing.Indexable$MyAccessor.index(Indexable.java:151)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.doIndex(RepositoryUpdater.java:1828)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.access$1400(RepositoryUpdater.java:1567)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.run(RepositoryUpdater.java:1748)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.run(RepositoryUpdater.java:1746)
   at org.netbeans.modules.parsing.impl.indexing.errors.TaskCache.refreshTransaction(TaskCache.java:460)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.index(RepositoryUpdater.java:1746)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.scanFiles(RepositoryUpdater.java:2131)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$FileListWork.getDone(RepositoryUpdater.java:2319)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.doTheWork(RepositoryUpdater.java:2179)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task._run(RepositoryUpdater.java:3853)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task.run(RepositoryUpdater.java:3791)
   at org.netbeans.modules.parsing.impl.TaskProcessor$CompilationJob.run(TaskProcessor.java:649)
   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:662)