Q31. How does Kotlin handle null safety?
Kotlin's type system distinguishes nullable from non-nullable types. `String` cannot hold null; `String?` can. This moves null checks to compile time and largely eliminat...
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Q32. What is the difference between value types and reference types?
Value types store their data directly and are copied on assignment. Reference types store a reference to heap data, and copying copies the reference. - Value types: numer...
Q33. What is the difference between a pointer and a reference?
A pointer is a variable that stores an address. It can be null, reassigned and used with pointer arithmetic. A reference is an alias for an existing object: it must be in...
Q34. What is ownership in Rust and why does the language need it?
Ownership is Rust's compile-time memory management model. Every value has exactly one owner, and when the owner goes out of scope the value is dropped and its memory free...
Q35. How do slices differ from arrays in Go?
An array has a fixed length that is part of its type: `[4]int` and `[5]int` are different types, and copying an array copies all elements. A slice is a small descriptor w...
Q36. A train travels 300 km in 3 hours, then 200 km in 2.5 hours. What is its average speed?
Average speed is total distance divided by total time, not the average of the two speeds. Total distance = 300 + 200 = 500 km. Total time = 3 + 2.5 = 5.5 hours. Average s...
Q37. Tell me about yourself.
Use a tight 60-90 second structure: Present, Past, Future. - Present: your current role and the core value you deliver ("I am a full-stack engineer with four years buildi...
Q38. What is the difference between a container and a virtual machine?
A VM virtualises hardware: each VM runs a full guest OS on a hypervisor, so it is heavy (GBs) and slow to boot (minutes) but strongly isolated. A container virtualises th...
Q39. Explain Big O notation with common complexities.
Big O describes how runtime or memory grows with input size, ignoring constants and lower-order terms. From fastest to slowest: - O(1) constant: hash lookup, array index....
Q40. What is the difference between an interface and an abstract class?
- An interface declares a contract. It supports abstract methods plus default and static methods (Java 8+), private methods (Java 9+) and constants. A class can implement...