About Question enthuware.ocpjp.v7.2.1437 :

[tn1408]

Hi Paul,

This is a very good question. I learned a few things with it.
However I believe #3 should also be a good answer.

Thanks,
Tony

[admin]

Option 3 is not syntactically correct. The explanation explains why it is not correct.
-Paul.

[tn1408]

I tested it and it didn't give me any problem:

Code: Select all

enum Title {
        MR("Mr. "), MRS("Mrs. "), MS("Ms. ");
        private String title;
        private Title(String s){
            title = s;}
        public String format(String first, String last){
            return title+" "+first+" "+last;
        } 
       
        class TestClass1{
            void someMethod()
            {
                System.out.println(MR.format("Rob", "Miller"));} 
        }
        
       public static void main(String[] args){
           TestClass1 tc1 = Title.MR. new TestClass1();
           tc1.someMethod();
       } 
    }

Thanks,

Tony

[admin]

That is because your code has TestClass1 as the inner class of the enum. The code in question doesn't have any inner class.

[SepticInsect]

What part in the Explanation explains why "System.out.println(MR.format("Rob", "Miller"));" is not valid?

[admin]

Title is missing. It says right below the option,"It must be Title.MR.format(...)."

HTH,
Paul.

[romsky]

One more important fact is that in switch statement it is used the short version :

Title a = ..;

switch(a) {
case MR : ... ; // OK
case Title.MR : ...; // Compile error
}

[PtFyEH]

When I use the import statement:

Code: Select all

import static com.some.place.Title.*;

This option (#3) seems to become valid:

Code: Select all

void someMethod(){System.out.println(MR.format("Rob", "Miller"));}

And in the question it says:

(Assume that Title is accessible wherever required.)

So it sounds to me that one can assume this import.

[admin]

Title is accessible, not Mr.

[krohani]

Hi Paul - Can you please explain why it is that in a switch statement you cannot use the name of the Enum (Title) but when calling enum methods you have to use both the Enum name and the enum constant type (Title.MR)? What is the reasoning behind this?

[admin]

Hi Paul - Can you please explain why it is that in a switch statement you cannot use the name of the Enum (Title) but when calling enum methods you have to use both the Enum name and the enum constant type (Title.MR)? What is the reasoning behind this?

I am afraid the exact reason can only be given by the authors of the Java language but I couldn't find the it mentioned in JLS.
I can only guess that it is because of some lexical parsing issue. But I could be wrong.
HTH,
Paul.

[krohani]

No worries, I asked because 1) i was just curious and 2) I figured the answer would help me remember these points better

[yuir12]

Hello, question. Can you please give an example on how to use Title2 and Title for below? Thanks.

Code: Select all

enum Title2 {    
   DR;    
   private Title t = Title.MR;    
   public String format(String s){ return t.format(s, s); }; 
}

[admin]

Not sure what you mean by how to use. You mean how to refer to them in some other class?

Post some code to show what exactly are you trying to get at.

[yuir12]

Is this like a nested enum? am not sure how to use this. Thanks.

[admin]

You can use the Title2 enum just like you use any other enum. Like this:

Code: Select all

void m(){
   Title2 t2 = Title2.DR;
   Title t1 = Title.MR;
}