Enum constants in Switch

[Prithvi Sehgal]

Hi,

I have a very stupid doubt in using enums in switch. I am really confused though.
This is a sample of code from K&B chapter 5

 
enum Color{red,green,blue}
public class SwitchEnum {
	public static void main(String[] args) {
		Color c = Color.green;
		switch(c){
		case red:
			System.out.println("I am red");
		case green:
			System.out.println("I am green");
		case blue:
			System.out.println("I am blue");
			default:
				System.out.println("Blah blah");
				
		}
	}
}

The output in this case is green. I read somewhere specification says that, if you have to use enum's as case
constant, you must specify them without fully qualified name. I am puzzled how compiler is interpreting red and
green and blue in this case as a case label.

Hope someone can clarify this confusion.

Thanks,

[Larry Chung]

From one perspective, the "red and green and blue" are interpreted by the compiler as legal enum constants because the variable c is of enum type Color. If you create another enum such as Direction and try it like so:

    
enum Direction{north, south,east,west}
.
.
.
              Color c = Color.green;
              Direction d = Direction.north; 

                switch(d){  
                case red:
                    System.out.println("I am red");  
                case green:  
                    System.out.println("I am green");  
                case blue:  
                    System.out.println("I am blue");  
                    default:  
                        System.out.println("Blah blah");  
                          
                }  

then the compiler will report that red and green and blue "cannot be resolved or is not a field" because the switch is now on Direction, not Color.

[Mykola Kurutin]

Prithvi Sehgal wrote:

 
enum Color{red,green,blue}
public class SwitchEnum {
	public static void main(String[] args) {
		Color c = Color.green;
		switch(c){
		case red:
			System.out.println("I am red");
		case green:
			System.out.println("I am green");
		case blue:
			System.out.println("I am blue");
			default:
				System.out.println("Blah blah");
				
		}
	}
}

The output in this case is green.

Here is the actual output:
I am green
I am blue
Blah blah

Don`t forget about break; at the end of each case.