He had previously admitted charges of theft, assault by beating, possession of cocaine, possession of a bladed article, using false registration plates on a car, and drink driving.
He was also disqualified from driving for three years and must pay £100 victim surcharge.
During the afternoon of 18 June Corbett entered a shop in Elms Vale Road, Dover, picked up a packet of biscuits and went to pay for them. When staff opened the till to get his change, Corbett reached into the till and grabbed around £60 in cash. As the staff called for help, Corbett ran out of the shop, punching the shop owner in the face as he left.
Kent Police officers attended the scene and reviewed CCTV of the incident. A short while later Corbett drove past and was recognised by officers who stopped him in Astor Avenue.
Officers found a quantity of cocaine along under the driver's seat and a nine inch knife in the footwell of the front passenger seat.
The number plate to his car had also been tampered with.
Corbett was also charged with drink driving after he was found to have 47 microgrammes of alcohol in 100millilitres of breath. The legal limit is 35 microgrammes.
During police interview Corbett admitted he had stolen the case and said he had an expensive cocaine addiction.
Investigating officer Detective Constable Ruth Goddard said: "Corbett carried out a string of offences during the course of one afternoon and when swiftly apprehended by officers, blamed his actions on his drug addiction.
"Like all drug-related crime, his actions had a knock-on effect on others, and I hope he considers that impact during his time in prison."
