You need to learn these Java concepts to learn and use Selenium:
- Condition statement and looping statement
- Exception Handling
- Methods of String class
- List and Set
- Upcasting and Runtime Polymorphism
- OOPs concepts with examples
I would recommend this Selenium Certification Course by Intellipaat to start a career as Selenium Tester.
Also, watch this video on the career scope of Selenium Testing: