Is there any way to revoke or update private key? Suppose my private key corresponding to an address is stolen. 
Is there any way to revoke private key or update the private key?
Generate a new private key, calculate its public key, derive an address from the pubKeyScript and forward your funds protected with your old,  compromised private key to the new address protected by your new private key.

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Simplified:

Send your funds to a new address generated in a secure environment (HWW, cold storage, etc.)