Override toString() of enum type

[emma roberts]

import java.util.Arrays;
public enum Priority {
ONE(1) { public String toString() { return "LOW"; } }, // (1)
TWO(2),
THREE(3) { public String toString() { return "NORMAL"; } }, // (2)
FOUR(4),
FIVE(5) { public String toString() { return "HIGH"; } }; // (3)
private int pValue;
Priority(int pValue) {
this.pValue = pValue;
}
public static void main(String[] args) {
System.out.println(Arrays.toString(Priority.values()));
}
}

i don't undrestand why it print [LOW, TW O, NORMAL, FOUR, HIGH] as result?

[Carey Brown]

What result are you wanting?

Interesting code there. I didn't think you could override toString() for each constant.

[emma roberts]

the result is [LOW, TWO, NORMAL, FOUR, HIGH]

[Rob Spoor]

emma roberts wrote:i don't undrestand why it print [LOW, TW O, NORMAL, FOUR, HIGH] as result?

Then what did you expect? For enums, the default toString() implementation returns the same as name(), which is the name you give the constant. For three of them you've overridden toString(), and the overidden result is what you're getting for those.

Carey Brown wrote:I didn't think you could override toString() for each constant.

It's unusual, but any non-final method can be overridden in the enum constant. That excludes methods like order(), name(), equals() and hashCode(), but not toString(). What you're effectively creating is an anonymous sub class of the enum type - the only possible way to extend an enum. This sub class follows all normal rules.

This possibility to sub classing is also why you normally shouldn't use getClass() on an enum constant but getDeclaringClass(). From it's javadoc:

Returns the Class object corresponding to this enum constant's enum type. Two enum constants e1 and e2 are of the same enum type if and only if e1.getDeclaringClass() == e2.getDeclaringClass(). (The value returned by this method may differ from the one returned by the Object.getClass() method for enum constants with constant-specific class bodies.)

[emma roberts]

therefore the toString() method of each constant enum is automatically executed  when Priority.values() is executed

[Campbell Ritchie]

emma roberts wrote:therefore the toString() method of each constant enum is automatically executed  when Priority.values() is executed

No, it is called by Arrays#toString().

[Rob Spoor]

Campbell is right. Priority.values() only returns an array of Priority, it doesn't call any instance methods.

[Paul Clapham]

Carey Brown wrote:I didn't think you could override toString() for each constant.

Sure, like Rob said you can override pretty much anything. You can even declare a method of the enum and then override it in each constant. I've done that. I have an enum which represents levels in a (biological) taxonomy and it has a method called canBeChildOf(the enum); each enum constant overrides that method to specify what other enum constants it can be a child of in the tree.

[Campbell Ritchie]

Paul Clapham wrote:. . . . You can even declare a method of the enum and then override it in each constant. . . . .

There is an example about arithmetic in the Java™ Language Specificatiaon showing you how to do that.

[Winston Gutkowski]

Check Rob's first reply. Commas don't work the way you (plainly) think they do, so you haven't overridden toString() for TWO and FOUR.

Winston