如何在非属性泛型类中覆盖 equals 方法？

Question

I have a generic class that has no attributes, but a method with generic type. How can I override the equals method for it?

   public Foo<T> {
       boolean method(T bar){
           if (bar instanceOf Boolean) // do something and return 
           if (bar instanceOf String) // do something and return
           return false;
       }
   }

And intuitional Foo<String> s and Foo<Boolean> b should be different, so how can I override the equals to reflect this? Or it is bad to write a class like this?

Answer 1

It seems to me that if there are no attributes (which I take to mean instance fields), then the class should probably not be capable of being instantiated and the methods should be declared static (like the Math class in the Java API). In any event I don't believe you would need to override equals since it doesn't seem likely you would compare multiple instances. You could do your example method as follows:

    public static <T> boolean method(T foo) {
        if (foo instanceof String) {
            System.out.println("You passed a string");
            return true;
        } 
        if (foo instanceof Integer) {
            System.out.println("You passed an integer");
            return true;
        }
        return false;
    }

But if you really want to override equals, you could do something like this.

@Override
public boolean equals(Object o) {
   return this == o;
}