Arrays Class in Java — Java Technical Interview Questions & Answers

Arrays Class in Java

Arrays Class in Java

  • Arrays Class is about Java arrays. An array is a fixed-size row of the same type. Index from 0. Length is a.length (a field, not a method). Last valid index is length - 1.
  • Create Arrays Class: int[] a = new int[5]; or int[] a = {10, 20, 30};. A 2D array is an array of arrays: int[][] m = {{1,2},{3,4}}; m[1][0] is 3. Jagged means rows can have different lengths.
  • Arrays Class size cannot grow. If you need grow/shrink, use ArrayList. Out of range → ArrayIndexOutOfBoundsException.
  • Let's take this on the board with one tiny Main class — no extra files. Arrays Class in Java — prints length 3, middle value 20, then all values. Start from main, go line by line, and stop at each print. That output is the proof for Arrays Class.

Technical Interview Tip: Contrast array vs ArrayList in one line.

Code Examples for Arrays Class in Java

Example

// Array demo
public class Main {
  public static void main(String[] args) {
    int[] nums = {10, 20, 30};
    System.out.println(nums.length);
    System.out.println(nums[1]);
    for (int n : nums) System.out.print(n + " ");
  }
}

Arrays Class in Java — prints length 3, middle value 20, then all values.

How to Explain Arrays Class in Java to an Interviewer

What is Arrays Class?

Arrays Class — array = fixed-size, same type, index from 0. Arrays Class — a.length is a field. Last index = length - 1. Arrays Class — 2D = array of arrays. Jagged = rows of different length.

Why do we use Arrays Class in Java?

Makes the program clearer or safer Arrays Class — array = fixed-size, same type, index from 0.

Write one small example of Arrays Class.

Show syntax Say what prints

What mistake do beginners make with Arrays Class?

Only the name, no example Arrays Class — a[a.length] crashes. Size cannot grow — use ArrayList.

Where is Arrays Class used in a real program?

Day-to-day Java code