======= AST Display =========================
Package
  ClassDeclList [1]
  . 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
=============================================