How to check caseOwner is a user or queue ??

A) By Querying Owner.Type Field:  

       [SELECT Id,CaseNumber,OwnerId,Owner.Name,Owner.Type FROM Case]

       OR

       for (Case objCase : Trigger.new)

{ 

        If (objCase.Owner.Type == User.sobjecttype) { /*  Code if Owner is User*/}

else{/*code if Owner is Queue*/ }

       }

Possible values of Owner.Type are 

     1. User 

     2. Queue

B) if(string.valueOf(c.OwnerId).startsWith('005')){//owner is User       }

     if(string.valueOf(c.OwnerId).startsWith('00G')){//owner is Queue}

C)for (Case objCase : Trigger.new)

{ 

        If (objCase.OwnerID.getsobjecttype() == User.sobjecttype) { /*  Code if Owner is User*/}

else{/*code if Owner is Queue*/ }

    }