Declare your class like this:
public class eOAuth {
    private eOAuth(){}
    public final static int    ECodeOauthInvalidGrant = 0x1;
    public final static int    ECodeOauthUnknown       = 0x10;
    public static GetSomeStuff(){}
}
and you can used without initialization:
if (value == eOAuth.ECodeOauthInvalidGrant)
    eOAuth.GetSomeStuff();