[antlr-interest] Bug? in 2.7.1: ASTNULLType

[gidadoifiok]

The doc says:
  /** There is only one instance of this class **/

But there is no constructor declared which means a default constructor
is provided.  If you do the following:

  System.out.println(new ASTNULLType().hashCode());
  System.out.println(new ASTNULLType().hashCode());
  System.out.println(new ASTNULLType().hashCode());

you will see something like this:

  4565111
  3615258
  2964388

Meaning that it is very possible to create different instances
(where as the intent was only to have one: a singleton)

I suggest the following in ASTNULLType 

public class ASTNULLType implements AST {
    public static final ASNTNULLType singleton = new ASTNULLType();
    private ASTNULLType() { }

Then whereever in code you want to use it, just refer to, e.g.

  public static ASTNULLType ASTNULL = ASTNULLType.singleton;

- Gidado


 

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