I know that Java enums are compiled to classes with private constructors and a bunch of public static members. When comparing two members of a given enum, I've always used .equals(), e.g.

public useEnums(SomeEnum a)
{
    if(a.equals(SomeEnum.SOME_ENUM_VALUE))
    {
        ...
    }
    ...
}

However, I just came across some code that uses the equals operator == instead of .equals():

public useEnums2(SomeEnum a)
{
    if(a == SomeEnum.SOME_ENUM_VALUE)
    {
        ...
    }
    ...
}

Which operator is the one I should be using?