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Java Array Questions With Solutions (Part 1) — QaTribe

By Ajit Marathe
6 Min Read
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Java Array Questions That Crack Interviews Fast

Introduction:

What are Java Array Questions?

Java Array questions are programming problems that test a candidate’s ability to manipulate, traverse, and optimize array-based data structures. They are frequently asked in coding interviews to evaluate problem-solving and logic-building skills.

In this guide, we cover 10 important Java array questions with clear descriptions, step-by-step logic, and complete Java implementations so you can confidently answer in interviews.

Interviewers use array-based questions to evaluate:

  • solving skills
  • Understanding of logic
  • Ability to optimize solutions

Struggling with Java Array questions in coding interview round?

You’re not alone. Arrays are one of the most commonly asked topics—but most candidates fail because they don’t practice real interview-level problems.

In this guide, you’ll learn:
✔ Real Java Array questions asked in coding interview round
✔ Step-by-step solutions with explanation
✔ Optimized approaches (O(n), O(log n))
✔ Patterns used by top companies

Let’s dive in 🚀

1. Find Maximum Element in Array

Description

This problem requires you to find the largest element in an array. It is one of the most basic questions that tests your understanding of array traversal and comparison.

Logic

  1. Assume first element as maximum
  2. Traverse the array
  3. Compare each element with max
  4. Update max if a larger value is found

Code

public class MaxElement {    
public static int findMax(int[] arr) {
        int max = arr[0];       
      for (int num : arr) {
            if (num > max) {
                max = num;
            }
        }
        return max;
    }    

        public static void main(String[] args) {
        int[] arr = {3, 5, 1, 9, 2}; // Input       
        System.out.println("Max Element: " + findMax(arr)); // Output : Max Element:9
    }
}

2. Find Minimum Element in Array

Description

In this problem, you need to find the smallest element in the array.

Logic

  1. Assume first element as minimum
  2. Traverse array
  3. Update minimum when smaller element found

Code

public class MinElement {    
public static int findMin(int[] arr) {
        int min = arr[0];        
      for (int num : arr) {
            if (num < min) {
                min = num;
            }
        }
        return min;
    }    

public static void main(String[] args) {
int[] arr = {3, 5, 1, 9, 2}; // Input       
System.out.println("Min Element: " + findMin(arr)); // Output : Min Element: 1
    }
}

3. Reverse an Array

Description:

Reverse the elements of an array so that the first element becomes the last.

Logic:

Use two pointers:

  • One at start
  • One at end
    Swap elements and move inward

Code:

import java.util.Arrays;
public class ReverseArray {    
   public static void reverse(int[] arr) {
        int left = 0;
        int right = arr.length - 1;       
      while (left < right) {
            int temp = arr[left];
            arr[left] = arr[right];
            arr[right] = temp;           
            left++;
            right--;
        }
    }    

public static void main(String[] args) {
int[] arr = {1, 2, 3, 4}; // Input    
 reverse(arr);       
System.out.println("Reversed Array: " + Arrays.toString(arr)); // Output: Reversed Array:4,3,2,1
    }
}

4. Find Second Largest Element

Description:

Find the second largest element in the array without sorting it.

Logic:

Maintain two variables:

  • max
  • second max

Code:

public class SecondLargest {    
public static int findSecondLargest(int[] arr) {
        int max = Integer.MIN_VALUE;
        int second = Integer.MIN_VALUE;       
        for (int num : arr) {
            if (num > max) {
                second = max;
                max = num;
            } else if (num > second && num != max) {
                second = num;
            }
        }
        return second;
    }   

 public static void main(String[] args) {
 int[] arr = {1, 5, 3, 9, 7}; // Input       
 System.out.println("Second Largest: " + findSecondLargest(arr)); // Output
    }
}

5. Remove Duplicates from Array

Description:

Remove duplicate elements and keep only unique values.

Logic:

Use LinkedHashSet to maintain order and uniqueness.

Code:

import java.util.*;
public class RemoveDuplicates {
    public static Set<Integer> removeDuplicates(int[] arr) {
        Set<Integer> set = new LinkedHashSet<>();        
        for (int num : arr) {
            set.add(num);
        }
        return set;
    }    


public static void main(String[] args) {
int[] arr = {1, 2, 2, 3, 4, 4}; // Input        
System.out.println("Unique Elements: " + removeDuplicates(arr)); // Output
    }
}

These types of Java Array Questions are commonly asked in interviews to test your understanding of array traversal and data manipulation.

6. Find Missing Number

Description:

Find the missing number from 1 to n.

Logic:

Use formula: n(n+1)/2 and subtract actual sum.

Code:

public class MissingNumber {
   public static int findMissing(int[] arr, int n) {
        int expectedSum = n * (n + 1) / 2;
        int actualSum = 0;        
for (int num : arr) {
            actualSum += num;
        }
        return expectedSum - actualSum;
    }  
  
public static void main(String[] args) {
int[] arr = {1, 2, 4, 5}; // Input        
System.out.println("Missing Number: " + findMissing(arr, 5)); // Output
    }
}

7. Move Zeros to End

Description:

Move all zeros to the end while maintaining the order of non-zero elements.

Logic:

Track non-zero elements and fill remaining with zeros.

Code:

import java.util.Arrays;
public class MoveZeros { 
public static void moveZeros(int[] arr) {
        int index = 0;       
        for (int num : arr) {
            if (num != 0) {
                arr[index++] = num;
            }
        }       
     while (index < arr.length) {
            arr[index++] = 0;
        }
    }    


public static void main(String[] args) {
int[] arr = {0, 1, 0, 3, 12}; // Input        
moveZeros(arr);       
System.out.println("Result: " + Arrays.toString(arr)); // Output
    }
}

In conclusion, mastering Java Array Questions is a crucial step toward cracking technical interviews. These Java Array Questions not only strengthen your fundamentals but also help you develop strong logical thinking skills.

8. Find Duplicate Element

Description:

Find the first duplicate element in the array.

Logic:

Use HashSet to track visited elements.

Code:

import java.util.*;
public class FindDuplicate {
   public static int findDuplicate(int[] arr) {
        Set<Integer> set = new HashSet<>();        
        for (int num : arr) {
            if (!set.add(num)) {
                return num;
            }
        }
        return -1;
    }    


public static void main(String[] args) {
int[] arr = {1, 3, 4, 2, 2}; // Input        
System.out.println("Duplicate: " + findDuplicate(arr)); // Output
    }
}

Java Array Questions are one of the most important topics in coding interviews. In this guide, we’ll cover real-time Java Array Questions with practical examples.

9. Two Sum Problem

Description:

Find two numbers whose sum equals a given target.

Logic:

Use HashMap to store visited elements and check complement.

Code:

import java.util.*;
public class TwoSum {    
public static void findPair(int[] arr, int target) {
        Map<Integer, Integer> map = new HashMap<>();        
        for (int num : arr) {
            int diff = target - num;            
            if (map.containsKey(diff)) {
                System.out.println("Pair: " + diff + ", " + num);
                return;
            }
            map.put(num, 1);
        }
    }    


public static void main(String[] args) {
        int[] arr = {2, 7, 11, 15}; // Input
        int target = 9;        
        findPair(arr, target); // Output
    }
}

10. Kadane’s Algorithm

Description:

Find the maximum sum of a contiguous subarray.

Logic:

Track current sum and maximum sum. Reset current sum when it becomes negative.

Code:

public class Kadane {    
public static int maxSubArray(int[] arr) {
        int max = arr[0];
        int current = arr[0];        
        for (int i = 1; i < arr.length; i++) {
            current = Math.max(arr[i], current + arr[i]);
            max = Math.max(max, current);
        }
        return max;
    }    

public static void main(String[] args) {
int[] arr = {-2,1,-3,4,-1,2,1,-5,4}; // Input        
System.out.println("Max Subarray Sum: " + maxSubArray(arr)); // Output
    }
}

Conclusion:

In this post, we covered the top 10 Java array problems with detailed explanations, clear logic, and clean Java implementations. Instead of memorizing solutions, focus on understanding the approach behind each problem. This will help you tackle variations of the same questions in interviews.

Consistency is the key. Practice these problems regularly, try writing the code without looking, and gradually move towards more complex problems. The more you practice, the more confident you will become during coding rounds.

By consistently practicing these Java Array Questions, you will become more confident in solving complex problems and performing well in coding rounds. Focus on understanding the logic behind each solution rather than memorizing answers, and you will see significant improvement.

Advanced Java Array Questions like these help interviewers evaluate how efficiently you handle real-world coding scenarios.

Common Patterns in Java Array Questions

  • Sliding Window
  • Two Pointer Technique
  • Prefix Sum
  • Kadane’s Algorithm

External Resources for Practice

Here are some high-quality resources where you can practice and deepen your understanding of Java array problems:

Final Tip

Don’t just read — code along.
Don’t just code — explain it out loud.
That’s how you crack interviews like a pro.

🔥 Continue Your Learning Journey

Want to go beyond Java Arrays Questions and crack interviews faster? Check these hand-picked guides:

👉 🚀 Master TestNG Framework (Enterprise Level)
Build scalable automation frameworks with CI/CD, parallel execution, and real-world architecture
➡️ Read: TestNG Automation Framework – Complete Architect Guide

👉 🧠 Learn Cucumber (BDD from Scratch to Advanced)
Understand Gherkin, step definitions, and real-world BDD framework design
➡️ Read: Cucumber Automation Framework – Beginner to Advanced Guide

👉 🔐 API Authentication Made Simple
Master JWT, OAuth, Bearer Tokens with real API testing examples
➡️ Read: Ultimate API Authentication Guide

👉 ⚡ Crack Playwright Interviews (2026 Ready)
Top real interview questions with answers and scenarios
➡️ Read: Playwright Interview Questions Guide

👉 🧠 Java Coding Interview Series
Look into our Java Coding Interview series:
➡️ Read: Java String coding Part-1
➡️ Read: Java Array coding Part-1
➡️ Read: Java Array Coding Part-2

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