Today I passed 1Z0-810 (Upgrade Java SE 7 to Java SE 8 OCP Programmer exam) with 79% marks (though I feel it is less then I expected).
I did 2 months (Jun & July) of hard study for achieving this with my regular office hours. I work 5 days a weeks but sometimes due to release schedule I also had to work over weekends and late nights so it was really challenging to find time for studying regularly.
Things I studied for preparing for exam were:
1. OCA Java SE 8 Programmer I Exam Guide (Exams 1Z0-808) - By: Kathy Sierra; Bert Bates
2. OCA: Oracle Certified Associate Java SE 8 Programmer I Study Guide: Exam 1Z0-808 - By: Jeanne Boyarsky; Scott Selikoff
3. Java 8 in Action: Lambdas, streams, and functional-style programming - By: Raoul-Gabriel Urma, Mario Fusco, and Alan Mycroft
4. Live Lessons: Java 8 Lambda Expressions and Streams - By: Marty Hall
5. Live Lessons: Core Java - By: Cay S. Horstmann
6. OCA/OCP Java SE 7 Programmer I & II Study Guide (Exams 1Z0-803 & 1Z0-804) - by Kathy Sierra
7. Exam 1Z0-810: Upgrade Java SE 7 to Java SE 8 OCP Programmer Study Guide - By Mikalai Zaikin
8. EnthuWare 3 tests for Upgrade To SE 8 From SE 7 1Z0-810