diff --git a/tool/playground/JavaParserLR.g4 b/tool/playground/JavaParserLR.g4
new file mode 100644
index 000000000..2e54ef940
--- /dev/null
+++ b/tool/playground/JavaParserLR.g4
@@ -0,0 +1,615 @@
+ūparser grammar JavaParserLR;
+options {tokenVocab=JavaLexer;}
+
+// starting point for parsing a java file
+/* The annotations are separated out to make parsing faster, but must be associated with
+   a packageDeclaration or a typeDeclaration (and not an empty one). */
+compilationUnit
+    :   annotations
+        (   packageDeclaration importDeclaration* typeDeclaration*
+        |   classOrInterfaceDeclaration typeDeclaration*
+        )
+    |   packageDeclaration? importDeclaration* typeDeclaration*
+    ;
+
+packageDeclaration
+    :   'package' qualifiedName ';'
+    ;
+
+importDeclaration
+    :   'import' 'static'? qualifiedName ('.' '*')? ';'
+    ;
+
+typeDeclaration
+    :   classOrInterfaceDeclaration
+    |   ';'
+    ;
+
+classOrInterfaceDeclaration
+    :   classOrInterfaceModifiers (classDeclaration | interfaceDeclaration)
+    ;
+
+classOrInterfaceModifiers
+    :   classOrInterfaceModifier*
+    ;
+
+classOrInterfaceModifier
+    :   annotation   // class or interface
+    |   'public'     // class or interface
+    |   'protected'  // class or interface
+    |   'private'    // class or interface
+    |   'abstract'   // class or interface
+    |   'static'     // class or interface
+    |   'final'      // class only -- does not apply to interfaces
+    |   'strictfp'   // class or interface
+    ;
+
+modifiers
+    :   modifier*
+    ;
+
+classDeclaration
+    :   normalClassDeclaration
+    |   enumDeclaration
+    ;
+
+normalClassDeclaration
+    :   'class' Identifier typeParameters?
+        ('extends' type)?
+        ('implements' typeList)?
+        classBody
+    ;
+
+typeParameters
+    :   '<' typeParameter (',' typeParameter)* '>'
+    ;
+
+typeParameter
+    :   Identifier ('extends' typeBound)?
+    ;
+
+typeBound
+    :   type ('&' type)*
+    ;
+
+enumDeclaration
+    :   ENUM Identifier ('implements' typeList)? enumBody
+    ;
+
+enumBody
+    :   '{' enumConstants? ','? enumBodyDeclarations? '}'
+    ;
+
+enumConstants
+    :   enumConstant (',' enumConstant)*
+    ;
+
+enumConstant
+    :   annotations? Identifier arguments? classBody?
+    ;
+
+enumBodyDeclarations
+    :   ';' (classBodyDeclaration)*
+    ;
+
+interfaceDeclaration
+    :   normalInterfaceDeclaration
+    |   annotationTypeDeclaration
+    ;
+
+normalInterfaceDeclaration
+    :   'interface' Identifier typeParameters? ('extends' typeList)? interfaceBody
+    ;
+
+typeList
+    :   type (',' type)*
+    ;
+
+classBody
+    :   '{' classBodyDeclaration* '}'
+    ;
+
+interfaceBody
+    :   '{' interfaceBodyDeclaration* '}'
+    ;
+
+classBodyDeclaration
+    :   ';'
+    |   'static'? block
+    |   modifiers memberDecl
+    ;
+
+memberDecl
+    :   genericMethodOrConstructorDecl
+    |   memberDeclaration
+    |   'void' Identifier voidMethodDeclaratorRest
+    |   Identifier constructorDeclaratorRest
+    |   interfaceDeclaration
+    |   classDeclaration
+    ;
+
+memberDeclaration
+    :   type (methodDeclaration | fieldDeclaration)
+    ;
+
+genericMethodOrConstructorDecl
+    :   typeParameters genericMethodOrConstructorRest
+    ;
+
+genericMethodOrConstructorRest
+    :   (type | 'void') Identifier methodDeclaratorRest
+    |   Identifier constructorDeclaratorRest
+    ;
+
+methodDeclaration
+    :   Identifier methodDeclaratorRest
+    ;
+
+fieldDeclaration
+    :   variableDeclarators ';'
+    ;
+
+interfaceBodyDeclaration
+    :   modifiers interfaceMemberDecl
+    |   ';'
+    ;
+
+interfaceMemberDecl
+    :   interfaceMethodOrFieldDecl
+    |   interfaceGenericMethodDecl
+    |   'void' Identifier voidInterfaceMethodDeclaratorRest
+    |   interfaceDeclaration
+    |   classDeclaration
+    ;
+
+interfaceMethodOrFieldDecl
+    :   type Identifier interfaceMethodOrFieldRest
+    ;
+
+interfaceMethodOrFieldRest
+    :   constantDeclaratorsRest ';'
+    |   interfaceMethodDeclaratorRest
+    ;
+
+methodDeclaratorRest
+    :   formalParameters ('[' ']')*
+        ('throws' qualifiedNameList)?
+        (   methodBody
+        |   ';'
+        )
+    ;
+
+voidMethodDeclaratorRest
+    :   formalParameters ('throws' qualifiedNameList)?
+        (   methodBody
+        |   ';'
+        )
+    ;
+
+interfaceMethodDeclaratorRest
+    :   formalParameters ('[' ']')* ('throws' qualifiedNameList)? ';'
+    ;
+
+interfaceGenericMethodDecl
+    :   typeParameters (type | 'void') Identifier
+        interfaceMethodDeclaratorRest
+    ;
+
+voidInterfaceMethodDeclaratorRest
+    :   formalParameters ('throws' qualifiedNameList)? ';'
+    ;
+
+constructorDeclaratorRest
+    :   formalParameters ('throws' qualifiedNameList)? constructorBody
+    ;
+
+constantDeclarator
+    :   Identifier constantDeclaratorRest
+    ;
+
+variableDeclarators
+    :   variableDeclarator (',' variableDeclarator)*
+    ;
+
+variableDeclarator
+    :   variableDeclaratorId ('=' variableInitializer)?
+    ;
+
+constantDeclaratorsRest
+    :   constantDeclaratorRest (',' constantDeclarator)*
+    ;
+
+constantDeclaratorRest
+    :   ('[' ']')* '=' variableInitializer
+    ;
+
+variableDeclaratorId
+    :   Identifier ('[' ']')*
+    ;
+
+variableInitializer
+    :   arrayInitializer
+    |   expression
+    ;
+
+arrayInitializer
+    :   '{' (variableInitializer (',' variableInitializer)* (',')? )? '}'
+    ;
+
+modifier
+    :   annotation
+    |   'public'
+    |   'protected'
+    |   'private'
+    |   'static'
+    |   'abstract'
+    |   'final'
+    |   'native'
+    |   'synchronized'
+    |   'transient'
+    |   'volatile'
+    |   'strictfp'
+    ;
+
+packageOrTypeName
+    :   qualifiedName
+    ;
+
+enumConstantName
+    :   Identifier
+    ;
+
+typeName
+    :   qualifiedName
+    ;
+
+type
+	:	classOrInterfaceType ('[' ']')*
+	|	primitiveType ('[' ']')*
+	;
+
+classOrInterfaceType
+	:	Identifier typeArguments? ('.' Identifier typeArguments? )*
+	;
+
+primitiveType
+    :   'boolean'
+    |   'char'
+    |   'byte'
+    |   'short'
+    |   'int'
+    |   'long'
+    |   'float'
+    |   'double'
+    ;
+
+variableModifier
+    :   'final'
+    |   annotation
+    ;
+
+typeArguments
+    :   '<' typeArgument (',' typeArgument)* '>'
+    ;
+
+typeArgument
+    :   type
+    |   '?' (('extends' | 'super') type)?
+    ;
+
+qualifiedNameList
+    :   qualifiedName (',' qualifiedName)*
+    ;
+
+formalParameters
+    :   '(' formalParameterDecls? ')'
+    ;
+
+formalParameterDecls
+    :   variableModifiers type formalParameterDeclsRest
+    ;
+
+formalParameterDeclsRest
+    :   variableDeclaratorId (',' formalParameterDecls)?
+    |   '...' variableDeclaratorId
+    ;
+
+methodBody
+    :   block
+    ;
+
+constructorBody
+    :   '{' explicitConstructorInvocation? blockStatement* '}'
+    ;
+
+explicitConstructorInvocation
+    :   nonWildcardTypeArguments? ('this' | 'super') arguments ';'
+    |   expression '.' nonWildcardTypeArguments? 'super' arguments ';'
+    ;
+
+qualifiedName
+    :   Identifier ('.' Identifier)*
+    ;
+
+literal
+    :   integerLiteral
+    |   FloatingPointLiteral
+    |   CharacterLiteral
+    |   StringLiteral
+    |   booleanLiteral
+    |   'null'
+    ;
+
+integerLiteral
+    :   HexLiteral
+    |   OctalLiteral
+    |   DecimalLiteral
+    ;
+
+booleanLiteral
+    :   'true'
+    |   'false'
+    ;
+
+// ANNOTATIONS
+
+annotations
+    :   annotation+
+    ;
+
+annotation
+    :   '@' annotationName ( '(' ( elementValuePairs | elementValue )? ')' )?
+    ;
+
+annotationName
+    : Identifier ('.' Identifier)*
+    ;
+
+elementValuePairs
+    :   elementValuePair (',' elementValuePair)*
+    ;
+
+elementValuePair
+    :   Identifier '=' elementValue
+    ;
+
+elementValue
+    :   expression
+    |   annotation
+    |   elementValueArrayInitializer
+    ;
+
+elementValueArrayInitializer
+    :   '{' (elementValue (',' elementValue)*)? (',')? '}'
+    ;
+
+annotationTypeDeclaration
+    :   '@' 'interface' Identifier annotationTypeBody
+    ;
+
+annotationTypeBody
+    :   '{' (annotationTypeElementDeclaration)* '}'
+    ;
+
+annotationTypeElementDeclaration
+    :   modifiers annotationTypeElementRest
+    ;
+
+annotationTypeElementRest
+    :   type annotationMethodOrConstantRest ';'
+    |   normalClassDeclaration ';'?
+    |   normalInterfaceDeclaration ';'?
+    |   enumDeclaration ';'?
+    |   annotationTypeDeclaration ';'?
+    ;
+
+annotationMethodOrConstantRest
+    :   annotationMethodRest
+    |   annotationConstantRest
+    ;
+
+annotationMethodRest
+    :   Identifier '(' ')' defaultValue?
+    ;
+
+annotationConstantRest
+    :   variableDeclarators
+    ;
+
+defaultValue
+    :   'default' elementValue
+    ;
+
+// STATEMENTS / BLOCKS
+
+block
+    :   '{' blockStatement* '}'
+    ;
+
+blockStatement
+    :   localVariableDeclarationStatement
+    |   classOrInterfaceDeclaration
+    |   statement
+    ;
+
+localVariableDeclarationStatement
+    :    localVariableDeclaration ';'
+    ;
+
+localVariableDeclaration
+    :   variableModifiers type variableDeclarators
+    ;
+
+variableModifiers
+    :   variableModifier*
+    ;
+
+statement
+    : block
+    |   ASSERT expression (':' expression)? ';'
+    |   'if' parExpression statement ('else' statement)?
+    |   'for' '(' forControl ')' statement
+    |   'while' parExpression statement
+    |   'do' statement 'while' parExpression ';'
+    |   'try' block
+        ( catches 'finally' block
+        | catches
+        | 'finally' block
+        )
+    |   'switch' parExpression '{' switchBlockStatementGroups '}'
+    |   'synchronized' parExpression block
+    |   'return' expression? ';'
+    |   'throw' expression ';'
+    |   'break' Identifier? ';'
+    |   'continue' Identifier? ';'
+    |   ';'
+    |   statementExpression ';'
+    |   Identifier ':' statement
+    ;
+
+catches
+    :   catchClause (catchClause)*
+    ;
+
+catchClause
+    :   'catch' '(' formalParameter ')' block
+    ;
+
+formalParameter
+    :   variableModifiers type variableDeclaratorId
+    ;
+
+switchBlockStatementGroups
+    :   (switchBlockStatementGroup)*
+    ;
+
+/* The change here (switchLabel -> switchLabel+) technically makes this grammar
+   ambiguous; but with appropriately greedy parsing it yields the most
+   appropriate AST, one in which each group, except possibly the last one, has
+   labels and statements. */
+switchBlockStatementGroup
+    :   switchLabel+ blockStatement*
+    ;
+
+switchLabel
+    :   'case' constantExpression ':'
+    |   'case' enumConstantName ':'
+    |   'default' ':'
+    ;
+
+forControl
+    :   enhancedForControl
+    |   forInit? ';' expression? ';' forUpdate?
+    ;
+
+forInit
+    :   localVariableDeclaration
+    |   expressionList
+    ;
+
+enhancedForControl
+    :   variableModifiers type Identifier ':' expression
+    ;
+
+forUpdate
+    :   expressionList
+    ;
+
+// EXPRESSIONS
+
+parExpression
+    :   '(' expression ')'
+    ;
+
+expressionList
+    :   expression (',' expression)*
+    ;
+
+statementExpression
+    :   expression
+    ;
+
+constantExpression
+    :   expression
+    ;
+
+expression
+	:   '(' expression ')'
+    |   'this' 
+    |   'super'
+    |   integerLiteral
+    |   Identifier
+    |   type '.' 'class'
+    |   expression '.' Identifier
+    |   expression '.' 'this'
+    |   expression '.' 'super' '(' expressionList? ')'
+    |   expression '.' 'new' Identifier '(' expressionList? ')'
+    |	creator
+//	|	'new' type ( '(' expressionList? ')' | ('[' expression ']')+)
+    |   expression '[' expression ']'
+    |   '(' type ')' expression
+    |   expression ('++' | '--')
+    |   expression '(' expressionList? ')'
+    |   ('+'|'-'|'++'|'--') expression
+    |   ('~'|'!') expression
+    |   expression ('*'|'/'|'%') expression
+    |   expression ('+'|'-') expression
+    |   expression ('<<' | '>>>' | '>>') expression
+    |   expression ('<=' | '>=' | '>' | '<') expression
+    |   expression 'instanceof' expression
+    |   expression ('==' | '=') expression
+    |   expression '&' expression
+    |   expression '^'<assoc=right> expression
+    |   expression '|' expression
+    |   expression '&&' expression
+    |   expression '||' expression
+    |   expression '?' expression ':' expression
+    |   expression
+    	('='<assoc=right>
+        |'+='<assoc=right>
+        |'-='<assoc=right>
+        |'*='<assoc=right>
+        |'/='<assoc=right>
+        |'&='<assoc=right>
+        |'|='<assoc=right>
+        |'='<assoc=right>
+        |'>' '>' '='<assoc=right>
+        |'>' '>' '>' '='<assoc=right>
+        |'<' '<' '='<assoc=right>
+        |'%='<assoc=right>
+        )
+        expression
+    ;
+
+creator
+    :   nonWildcardTypeArguments createdName classCreatorRest
+    |   createdName (arrayCreatorRest | classCreatorRest)
+    ;
+
+createdName
+    :   classOrInterfaceType
+    |   primitiveType
+    ;
+
+innerCreator
+    :   nonWildcardTypeArguments? Identifier classCreatorRest
+    ;
+
+arrayCreatorRest
+    :   '['
+        (   ']' ('[' ']')* arrayInitializer
+        |   expression ']' ('[' expression ']')* ('[' ']')*
+        )
+    ;
+
+classCreatorRest
+    :   arguments classBody?
+    ;
+
+nonWildcardTypeArguments
+    :   '<' typeList '>'
+    ;
+
+arguments
+    :   '(' expressionList? ')'
+    ;