Primitive versus reference types, why Java is always pass-by-value, wrapper classes with autoboxing, the Integer cache trap, overflow and floating-point surprises, and var.
Why Java strings are immutable, how the String Constant Pool works, == versus equals, intern, StringBuilder versus StringBuffer, and the string methods interviewers expect you to know.
The collections hierarchy, ArrayList versus LinkedList, Set and Map implementations, how HashMap works internally in Java 8 and later, Comparable versus Comparator, and fail-fast iterators.
Why generics exist, generic methods and bounded types, type erasure and what it prevents, invariance, wildcards, and the PECS rule explained with a working example.
What freshers are asked in Java interviews, how to set up a practice project in a minute, a 30-day study plan that covers every step of this collection, and a daily routine that fits 60 to 90 minutes.
How a stream pipeline works, intermediate versus terminal operations, lazy evaluation, map versus flatMap, grouping with Collectors, why a stream cannot be reused, and when parallel streams hurt.
Creating threads, why start() and run() differ, race conditions and how synchronized, AtomicInteger and volatile fix them, deadlock and lock ordering, BlockingQueue for producer-consumer, and thread states.
How Java talks to a relational database with JDBC, why PreparedStatement beats Statement, how SQL injection works and is prevented, transactions with commit and rollback, batching, and connection pooling.
What generics are, why List of T beats collections of object, generic constraints, and a short introduction to covariance.
Dependency injection and service lifetimes (transient, scoped, singleton), the five SOLID principles with small examples, and unit testing with xUnit and the Arrange-Act-Assert pattern.
The 25 mistakes that cost freshers the most marks in C# and .NET interviews, grouped by topic, with what to say or write instead.
The 50 most-asked C# and .NET interview questions for freshers, grouped by topic and marked High, Medium or Low priority, each with a short answer you can say out loud.