Sample Code:
Account acc = new Account(Name = 'Account Name', Phone = '8888888888', Industry = 'Agriculture'); //Code to convert Account to JSON string String str = JSON.serialize(acc); system.debug('Account JSON Data - ' + str); //Code to convert JSON string to Account Account acc1 = (Account)JSON.deserialize(str, Account.Class); system.debug('Account Data - ' + acc1);