Why can't enum constructors be protected or public in Java?

Question

The whole question is in the title. For example:

enum enumTest {          TYPE1(4.5, "string1"), TYPE2(2.79, "string2");         double num;         String st;          enumTest(double num, String st) {             this.num = num;             this.st = st;         }     } 

The constructor is fine with the default or private modifier, but gives me a compiler error if given the public or protected modifiers.

Answer 1

Think of Enums as a class with a finite number of instances. There can never be any different instances beside the ones you initially declare.

Thus, you cannot have a public or protected constructor, because that would allow more instances to be created.

Note: this is probably not the official reason. But it makes the most sense for me to think of enums this way.

Answer 2

Because you cannot call the constructor yourself.

Here is what the tutorials on Enums has to say:

Note: The constructor for an enum type must be package-private or private access. It automatically creates the constants that are defined at the beginning of the enum body. You cannot invoke an enum constructor yourself.