Annotations Arrays & Multidimensional Arrays Build Tools: Maven & Gradle Class Loading & Bytecode Verification Collections Framework Concurrency & Threads Design Patterns in Java Enums equals(), hashCode() & toString() Contracts Exceptions Functional Interfaces & Method References Garbage Collection Generics I/O & NIO Inner Classes & Anonymous Classes Interfaces & Abstract Classes Java Date & Time API (java.time) Java Fundamentals: Syntax, Data Types & Operators Java Networking & HTTP Client Java Platform Module System (JPMS) JDBC & Database Connectivity JVM, JRE & Memory Logging in Java (java.util.logging, SLF4J, Log4j) Object Cloning & Copy Semantics OOP & Classes Optional & Null Safety Pattern Matching & Switch Expressions Records & Sealed Classes Reflection API Regular Expressions in Java Serialization & Deserialization Static & Instance Initialization Blocks Streams & Lambdas String Handling, StringBuilder & Immutability Unit Testing with JUnit & Mockito Varargs, Autoboxing & Unboxing