Java Collections Framework:

• ArrayList
• LinkedList
• HashMap
• HashSet
• ArrayDeque

Core Java:

• Exceptions handling
• Lambda expression
• Stream

Testing Frameworks:

• Unit tests:
  • JUnit
  • Mockito
• Integration tests:
  • Selenium WebDriver

Design principles:

• SOLID
• DRY
• Clean code

Design patterns:

• Singleton
• Prototype
• Strategy
• Factory
• Builder
• Facade
• Decorator
• Observer
• Adapter

Database (MySQL):

• Stored procedures
• Functions
• Triggers
• Events

Spring Framework:

• Beans
• Components
• Dependency Injection

Hibernate Framework:

• Entities
• Entity relationships
• HQL:
  • Named Queries
  • Named Native Queries

Thymeleaf Framework:

• Sending mails
• Mail templates