======= AST Display =========================
Package
  ClassDeclList [2]
  . ClassDecl
  .   "MainClass" classname
  .   FieldDeclList [0]
  .   MethodDeclList [1]
  .   . (public static) MethodDecl
  .   .   VOID BaseType
  .   .   "main" methodname
  .   .   ParameterDeclList [1]
  .   .   . ParameterDecl
  .   .   .   ArrayType
  .   .   .     ClassType
  .   .   .       "String" classname
  .   .   .   "args"parametername 
  .   .   StmtList [1]
  .   .   . VarDeclStmt
  .   .   .   VarDecl
  .   .   .     ClassType
  .   .   .       "SecondSubClass" classname
  .   .   .     "newobj" varname
  .   .   .   NewObjectExpr
  .   .   .     ClassType
  .   .   .       "SecondSubClass" classname
  . ClassDecl
  .   "SuperClass" classname
  .   FieldDeclList [0]
  .   MethodDeclList [1]
  .   . (private) MethodDecl
  .   .   VOID BaseType
  .   .   "fillup" methodname
  .   .   ParameterDeclList [4]
  .   .   . ParameterDecl
  .   .   .   BOOLEAN BaseType
  .   .   .   "open"parametername 
  .   .   . ParameterDecl
  .   .   .   ArrayType
  .   .   .     INT BaseType
  .   .   .   "jar"parametername 
  .   .   . ParameterDecl
  .   .   .   INT BaseType
  .   .   .   "marble"parametername 
  .   .   . ParameterDecl
  .   .   .   INT BaseType
  .   .   .   "upto"parametername 
  .   .   StmtList [2]
  .   .   . VarDeclStmt
  .   .   .   VarDecl
  .   .   .     INT BaseType
  .   .   .     "index" varname
  .   .   .   LiteralExpr
  .   .   .     "0" IntLiteral
  .   .   . IfStmt
  .   .   .   BinaryExpr
  .   .   .     "==" Operator
  .   .   .       RefExpr
  .   .   .         IdRef
  .   .   .           "open" Identifier
  .   .   .       LiteralExpr
  .   .   .         "true" BooleanLiteral
  .   .   .   BlockStmt
  .   .   .     StatementList [1]
  .   .   .     . WhileStmt
  .   .   .     .   BinaryExpr
  .   .   .     .     "<" Operator
  .   .   .     .       RefExpr
  .   .   .     .         IdRef
  .   .   .     .           "index" Identifier
  .   .   .     .       RefExpr
  .   .   .     .         IdRef
  .   .   .     .           "upto" Identifier
  .   .   .     .   BlockStmt
  .   .   .     .     StatementList [2]
  .   .   .     .     . AssignStmt
  .   .   .     .     .   IndexedRef
  .   .   .     .     .     RefExpr
  .   .   .     .     .       IdRef
  .   .   .     .     .         "index" Identifier
  .   .   .     .     .     IdRef
  .   .   .     .     .       "ownjar" Identifier
  .   .   .     .     .   RefExpr
  .   .   .     .     .     IndexedRef
  .   .   .     .     .       RefExpr
  .   .   .     .     .         IdRef
  .   .   .     .     .           "index" Identifier
  .   .   .     .     .       IdRef
  .   .   .     .     .         "jar" Identifier
  .   .   .     .     . AssignStmt
  .   .   .     .     .   IndexedRef
  .   .   .     .     .     RefExpr
  .   .   .     .     .       IdRef
  .   .   .     .     .         "index" Identifier
  .   .   .     .     .     IdRef
  .   .   .     .     .       "jar" Identifier
  .   .   .     .     .   RefExpr
  .   .   .     .     .     IdRef
  .   .   .     .     .       "marble" Identifier
=============================================