title: GWT Compilation error in Eclipse Oxygen
body: <p>I'm getting these weird errors when I try to compile my Libgdx game to HTML5 in Eclipse.</p>
  
  <pre><code>Tracing compile failure path for type 'java.util.function.DoubleUnaryOperator'
       [ERROR] Errors in 'com/google/gwt/emul/java/util/function/DoubleUnaryOperator.java'
       [ERROR] Line 33: Default methods are allowed only at source level 1.8 or above
       [ERROR] Line 35: Cannot refer to the non-final local variable after defined in an enclosing scope
       [ERROR] Line 40: Cannot refer to the non-final local variable before defined in an enclosing scope
       [ERROR] Line 40: Lambda expressions are allowed only at source level 1.8 or above
       [ERROR] Line 35: Lambda expressions are allowed only at source level 1.8 or above
       [ERROR] Line 38: Default methods are allowed only at source level 1.8 or above
       [ERROR] Line 27: Illegal modifier for the interface method identity; only public &amp; abstract are permitted
       [ERROR] Line 27: Static methods are allowed in interfaces only at source level 1.8 or above
       [ERROR] Line 28: Lambda expressions are allowed only at source level 1.8 or above
  Tracing compile failure path for type 'java.util.stream.Collectors'
    [ERROR] Errors in 'com/google/gwt/emul/java/util/stream/Collectors.java'
       [ERROR] Line 291: This static method of interface Collector can only be accessed as Collector.of
       [ERROR] Line 348: Lambda expressions are allowed only at source level 1.8 or above
       [ERROR] Line 96: Lambda expressions are allowed only at source level 1.8 or above
       [ERROR] Line 223: The method of(Supplier&lt;R&gt;, BiConsumer&lt;R,T&gt;, BinaryOperator&lt;R&gt;, Collector.Characteristics...) in the type Collector is not applicable for the arguments (() -&gt; {}, (&lt;no type&gt; u, &lt;no type&gt; t) -&gt; {}, (Object[] u1, Object[] u2) -&gt; {}, (Object[] a) -&gt; {})
       [ERROR] Line 311: Constructor references are allowed only at source level 1.8 or above
       [ERROR] Line 192: Method references are allowed only at source level 1.8 or above
       [ERROR] Line 205: Lambda expressions are allowed only at source level 1.8 or above
       [ERROR] Line 143: Constructor references are allowed only at source level 1.8 or above
       [ERROR] Line 168: Lambda expressions are allowed only at source level 1.8 or above
       [ERROR] Line 339: Lambda expressions are allowed only at source level 1.8 or above...
  </code></pre>
  
  <p>In my build.gradle, I've checked that the gwtVersion is using 2.7.0 and my sourceCompatibility is at 1.8. I've been at this thing for days and I can't seem to figure it out.</p>
  
  <p>Help!!!</p>
  
  <p><strong>UPDATED</strong></p>
  
  <p>Thank you Colin for the feedback. Here's the error I'm getting now:</p>
  
  <blockquote>
    <p>[ERROR] An internal compiler exception occurred
    com.google.gwt.dev.jjs.InternalCompilerException: Error constructing Java AST
        at com.google.gwt.dev.jjs.impl.GwtAstBuilder.translateException(GwtAstBuilder.java:3099)
        at com.google.gwt.dev.jjs.impl.GwtAstBuilder$AstVisitor.endVisit(GwtAstBuilder.java:352)
        at org.eclipse.jdt.internal.compiler.ast.AllocationExpression.traverse(AllocationExpression.java:670)
        at org.eclipse.jdt.internal.compiler.ast.ReturnStatement.traverse(ReturnStatement.java:373)
        at org.eclipse.jdt.internal.compiler.ast.MethodDeclaration.traverse(MethodDeclaration.java:347)
        at org.eclipse.jdt.internal.compiler.ast.TypeDeclaration.traverse(TypeDeclaration.java:1379)
        at com.google.gwt.dev.jjs.impl.GwtAstBuilder.process(GwtAstBuilder.java:3058)
        at com.google.gwt.dev.javac.CompilationStateBuilder$CompileMoreLater$UnitProcessorImpl.process(CompilationStateBuilder.java:141)
        at com.google.gwt.dev.javac.JdtCompiler$CompilerImpl.process(JdtCompiler.java:384)
        at org.eclipse.jdt.internal.compiler.Compiler.compile(Compiler.java:470)
        at com.google.gwt.dev.javac.JdtCompiler.doCompile(JdtCompiler.java:985)
        at com.google.gwt.dev.javac.CompilationStateBuilder$CompileMoreLater.compile(CompilationStateBuilder.java:339)
        at com.google.gwt.dev.javac.CompilationStateBuilder.doBuildFrom(CompilationStateBuilder.java:580)
        at com.google.gwt.dev.javac.CompilationStateBuilder.buildFrom(CompilationStateBuilder.java:513)
        at com.google.gwt.dev.javac.CompilationStateBuilder.buildFrom(CompilationStateBuilder.java:499)
        at com.google.gwt.dev.cfg.ModuleDef.getCompilationState(ModuleDef.java:668)
        at com.google.gwt.dev.Precompile.precompile(Precompile.java:255)
        at com.google.gwt.dev.Precompile.precompile(Precompile.java:229)
        at com.google.gwt.dev.Precompile.precompile(Precompile.java:145)
        at com.google.gwt.dev.Compiler.run(Compiler.java:206)
        at com.google.gwt.dev.Compiler.run(Compiler.java:158)
        at com.google.gwt.dev.Compiler$1.run(Compiler.java:120)
        at com.google.gwt.dev.CompileTaskRunner.doRun(CompileTaskRunner.java:55)
        at com.google.gwt.dev.CompileTaskRunner.runWithAppropriateLogger(CompileTaskRunner.java:50)
        at com.google.gwt.dev.Compiler.main(Compiler.java:127)
    Caused by: java.lang.NullPointerException
        at com.google.gwt.dev.jjs.impl.ReferenceMapper.get(ReferenceMapper.java:99)
        at com.google.gwt.dev.jjs.impl.GwtAstBuilder$AstVisitor.pushNewExpression(GwtAstBuilder.java:2642)
        at com.google.gwt.dev.jjs.impl.GwtAstBuilder$AstVisitor.endVisit(GwtAstBuilder.java:350)
        ... 23 more
       [ERROR] at TimeZone.java(126): new String(data)
          org.eclipse.jdt.internal.compiler.ast.AllocationExpression</p>
  </blockquote>
  
  <p>Maybe I have to update it to GWT 2.8.0?</p>
  
  <p>P.S: In my html\war\WEB-INF\lib directory, i have the following jars:</p>
  
  <p><a href="https://i.stack.imgur.com/NUOwM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/NUOwM.png" alt="enter image description here"></a></p>
  
  <p>Is that setup correct?</p>
  
  <p>UPDATED:</p>
  
  <p>Now updated to GWT 2.8.1. Now I get the following error:</p>
  
  <pre><code>Exception in thread "main" java.lang.NoSuchMethodError: com.google.gwt.util.regexfilter.RegexFilter: method &lt;init&gt;()V not found
  at com.google.gwt.util.regexfilter.WhitelistRegexFilter.&lt;init&gt;(WhitelistRegexFilter.java:21)
  at com.google.gwt.dev.jjs.JJSOptionsImpl.&lt;init&gt;(JJSOptionsImpl.java:54)
  at com.google.gwt.dev.PrecompileTaskOptionsImpl.&lt;init&gt;(PrecompileTaskOptionsImpl.java:39)
  at com.google.gwt.dev.CompilerOptionsImpl.&lt;init&gt;(CompilerOptionsImpl.java:30)
  at com.google.gwt.dev.Compiler.main(Compiler.java:108)
  </code></pre>
  
  <p>Should I clean up the (or some of the) jars that's in my html\war\WEB-INF\lib directory and use other jars?</p>