1Z0-803 and 1Z0-804 are exam numbers not certifications. Certifications require that you pass one or more exams and fulfill any other requirements (prior certifications, training, etc).
You can take the exams in any order you would like. You will only get the certification when you fulfill all the requirements of the certification. If you want to get the Oracle Certified Professional Java SE 7 Programmer certification, you'd need to pass both 1Z0-803 and 1Z0-804. You can do that by passing the 804 exam first and the 803 exam second but that doesn't seem particularly useful. You could also get one of the earlier OCP SE6 Programmer certifications and then take the upgrade exam to SE7.