Reverse an Array in Java — Java Technical Interview Questions & Answers

Reverse an Array in Java

Reverse an Array in Java

  • Reverse an Array 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 Reverse an Array: 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.
  • Reverse an Array 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. Reverse an Array in Java — two-pointer swap reverses to 4 3 2 1. Start from main, go line by line, and stop at each print. That output is the proof for Reverse an Array.
  index →  0    1    2
  array → [10,  20,  30]
           ↑         ↑
         first   length-1

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

Code Examples for Reverse an Array in Java

Example

public class Main {
  public static void main(String[] args) {
    int[] a = {1, 2, 3, 4};
    for (int i = 0, j = a.length - 1; i < j; i++, j--) {
      int t = a[i];
      a[i] = a[j];
      a[j] = t;
    }
    for (int x : a) System.out.print(x + " ");
  }
}

Reverse an Array in Java — two-pointer swap reverses to 4 3 2 1.

How to Explain Reverse an Array in Java to an Interviewer

What is Reverse an Array?

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

Why do we use Reverse an Array in Java?

Makes the program clearer or safer Reverse an Array — array = fixed-size, same type, index from 0.

Write one small example of Reverse an Array.

Show syntax Say what prints

What mistake do beginners make with Reverse an Array?

Only the name, no example Reverse an Array — a[a.length] crashes. Size cannot grow — use ArrayList.

Where is Reverse an Array used in a real program?

Day-to-day Java code