I see that you are now offline and wanted to get this information to you as soon as possible.
There are various causes for throwing up in cats, and if this has been going on all day or even for a few hours, your cat can become quickly dehydrated and the cause of the problem must be diagnosed and treated. The vet will be able to give him an injection of an anti-nausea/anti-emetic medication to help him feel better.
Because he's a male, if you haven't noticed him urinating recently, he may have a serious urethral obstruction and this will cause him to have no appetite, throw up, and become lethargic. This condition needs immediate veterinary treatment.http://www.sniksnak.com/cathealth/urethral.html
He might also have an intestinal obstruction which is not allowing him to defecate and toxins are building up in his system.
Your cat may have ingested a toxic or other non-food substance and this is causing his vomiting or he might have developed a viral or bacterial infection in his system.http://www.sniksnak.com/cathealth/vomiting.html
When a cat doesn't eat, even for a short period of time, he risks developing a serious liver condition called hepatic lipidosis, so it's important to have your kitty evaluated in person by a vet, immediately, to determine the cause of the vomiting and have him treated. If your vet does not have hours on the weekend, bring your cat to the nearest ER vet center for treatment.
I hope all will be well with your furry boy!
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