Java Varargs — Java Technical Interview Questions & Answers

Java Varargs

Java Varargs

  • Varargs is modern Java (5/8 toolkit). Lambdas are short functions: (n) -> print. They implement a functional interface (one abstract method). Streams let you filter/map/collect a list without a manual loop.
  • For Varargs: generics keep types safe: List<String>. Autoboxing turns int into Integer when needed. varargs is String... args. Optional avoids some null checks — don’t overuse it.
  • Keep Varargs small. Don’t dump business logic inside forEach. Know one tiny example you can write from memory.
  • Let's take this on the board with one tiny Main class — no extra files. Java Varargs — output: 10. sum(2, 3, 5) — varargs is a real int[] behind the scenes. 2+3+5=10. Start from main, go line by line, and stop at each print. That output is the proof for Varargs.

Technical Interview Tip: Explain Java Varargs as: definition → why → one code idea.

Code Examples for Java Varargs

Example

public class Main {
  static int sum(int... n) {
    int s = 0;
    for (int x : n) s += x;
    return s;
  }
  public static void main(String[] args) {
    System.out.println(sum(2, 3, 5));
  }
}

Java Varargs — output: 10. sum(2, 3, 5) — varargs is a real int[] behind the scenes. 2+3+5=10.

How to Explain Java Varargs to an Interviewer

What is Varargs?

Varargs is part of modern Java (generics / Java 8 style). Varargs — lambda = (args) -> body on a functional interface. Varargs — streams filter/map/collect. Generics = List<String>.

Why do we use Varargs in Java?

Makes the program clearer or safer Varargs is part of modern Java (generics / Java 8 style).

Write one small example of Varargs.

Show syntax Say what prints

What mistake do beginners make with Varargs?

Only the name, no example Varargs — huge logic inside lambdas, or forgetting generics.

Where is Varargs used in a real program?

Day-to-day Java code