What is Java, JVM, JDK, JRE and how Java programs run.

Primitive types, reference types, declaration, literals.

Arithmetic, relational, logical, bitwise, assignment and ternary operators.

Conditionals and loops: if-else, switch, for, while, do-while.

Declaring, initializing and iterating arrays.

Immutable String, mutable StringBuilder/StringBuffer, string methods, constant pool and StringReader

Basic sorting algorithms, hashing via hashCode/equals, and recursion patterns.

Bitwise operators, bit manipulation tricks, and Big-O complexity analysis.