CODEWITHSUNDEEP
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user3663882
user3663882

Reputation: 7357

Order of list's elements

Consider the following enum:

public enum Type{
     INTEGER,
     DOUBLE,
     BOOLEAN
}

Now, I have the following line:

List<Type> types = Arrays.asList(Type.values());

Do the list contains the elements in the same order they put into the enum? Is this order reliable?

Upvotes: 3

Views: 181

Answers (3)

Magnilex
Magnilex

Reputation: 11978

Yes. The Java Language Specification for Enums states:

/**
* 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();

It will returned an array with the constants as they are declared.

Regarding the Arrays.asList() method, you can rely on its order as well:

Returns a fixed-size list backed by the specified array. (Changes to the returned list "write through" to the array.)

Consider the below example, which is a very common way to initialize a List:

List<String> stooges = Arrays.asList("Larry", "Moe", "Curly");

The order of the list will be the same as in the array.

Upvotes: 4

David Soroko
David Soroko

Reputation: 9086

The JLS mentions that values() "Returns an array containing the constants of this enum type, in the order they're declared." (http://docs.oracle.com/javase/specs/jls/se8/html/jls-8.html#jls-8.9). So yes, you can assume that the order will be the same as long as your enum type doesn't change

For some details see How is values() implemented for Java 6 enums?

Upvotes: 2

AnkeyNigam
AnkeyNigam

Reputation: 2820

If you want to maintain Order of Elements use LinkedList: -

List<Type> types = new LinkedList<Type>(Arrays.asList(Type.values()));

Upvotes: 0

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