Doubt in Rules Roundup switch int only (enum works)

[Kaydell Leavitt]

You can not only switch on an int or a compatible type (byte or short) but you can now switch on an enumerated type created with the enum keyword.



Kaydell

[ June 07, 2007: Message edited by: Kaydell Leavitt ]
[ June 07, 2007: Message edited by: Kaydell Leavitt ]

[Chandra Bhatt]

I agree!

ublic class TestSwitch {
enum Color {RED,BLUE,GREEN,BLACK}

public static void main(String... args) {
Color c = Color.GREEN;

switch(c) {
case RED:
System.out.println("RED");break;
case BLUE:
System.out.println("BLUE"); break;
case GREEN:
System.out.println("GREEN"); break;
case BLACK:
System.out.println("BLACK"); break;
}

}
}

Thanks,

[Cor Takken]

My guess is that the switch uses the Enum.ordinal() method to get to an int value under the covers. That makes the Enum value an int value and thus valid for the switch-function.

But I might be wrong....

Cor

[Kaydell Leavitt]

My guess is that the switch uses the Enum.ordinal() method to get to an int value under the covers.

You may be able to convert an Enum to an int, but an Enum is really an instance of a subclass of Enum. An Enum is not compatible with an int and that's a good thing so that you don't accidentally pass an int constant where it isn't appropriate. With enum values, if you try to pass them as parameters where an int is required, you get a compile-time error.

Kaydell

[Kaydell Leavitt]

I believe that you can switch on the following types:

byte, short, int, char, and enum

Kaydell

[Sergio Tridente]

int i = (int)Thread.State.RUNNABLE;

It does not compile!

[Amit Ghorpade]

Hi,
even i have learnt this new thing that Enum works with switch
so far even i thought that only int compatible types work with switch.

Thanks

[Cor Takken]

Originally posted by Sergio Tridente:

int i = (int)Thread.State.RUNNABLE;

It does not compile!

Try

int i = Thread.State.RUNNABLE.ordinal();

Cor
[ June 12, 2007: Message edited by: Cor Takken ]