where is Enum.values() defined?

Question

Hi,

Every Java enumeration has a static values() method can be used like this

for (MyEnum enum : MyEnum.values()) {
    // Do something with enum
}

However, I cannot figure out where this method is defined. There's no mention of it in the Javadoc and it doesn't appear anywhere in the source file.

Answer 1

It's not explicitly defined, just like length property of java array is not defined. It is implicitly available for concrete Enum type.

Answer 2

It's defined in the JLS, section 8.9 "Enums"

Answer 3

This is required by the Java Language Specification: values and valueOf will be implicitly declared for all Enums:

/**
* Returns an array containing the constants of this enum 
* type, in the order they're declared.  This method may be
* used to iterate over the constants as follows:
*
*    for(E c : E.values())
*        System.out.println(c);
*
* @return an array containing the constants of this enum 
* type, in the order they're declared
*/
public static E[] values();

/**
* Returns the enum constant of this type with the specified
* name.
* The string must match exactly an identifier used to declare
* an enum constant in this type.  (Extraneous whitespace 
* characters are not permitted.)
* 
* @return the enum constant with the specified name
* @throws IllegalArgumentException if this enum type has no
* constant with the specified name
*/
public static E valueOf(String name);

These methods are added during compile time, so if you use javap to disassemble the code, you can actually look at their body.