Are you looking for Java coding challenges to sharpen your problem-solving skills? Do you want to take your Java learning journey to the next level?
Well then, you have come to the right place! We have a list of coding challenges that are both for beginners and advanced programmers. Are you eager to know about these challenges?
Before diving into these challenges, it’s helpful to have a solid understanding of method signatures in Java and how they impact function overloading and polymorphism. Mastering these concepts can make solving coding problems much easier.
So, without any further discussion, let us get into the topic at hand!
Summary Of The Article:
Solving coding challenges is an important part of learning any programming language. There may exist a lot of solutions to solve different exercises.
They help you to develop your logic-building skills. This makes the process more rich and helps you to grasp each and every concept you have learned.
Java programming language is a vast and detailed language, the more you code in it, the better you become.
You can solve these problems on online coding platforms and compete against other programmers.
If you solve challenges and write your own Java programs, you will find it easier to work on bigger projects as they will help you to clear the basic concepts of Java.
12 Java Programming Exercises and Challenges For Practice!
So you are learning Java programming language and want to start implementing all the fundamentals you have grasped? Do you want to know where to practice coding challenges? Worry not! We have a list of exercises that can help you build your technical skills.
Ready to get started? Then Let’s have a look!
String Manipulation Challenges in Java Programming For Beginners
A string in Java is a data type that represents a sequence of characters. You can say that a string is an organized series of characters. We can perform various operations on strings. Some of the basic challenges for string manipulation are given below.
1. String Reversal
In this challenge, you have to input a string and write a code that reverses its sequence. The string may or may not contain some spaces. Try to implement this code without using the reverse method provided by the Java string class.
For example, If the input string is “Welcome to CodingZap” your code should give the output “paZgnidoC ot emocleW” You can create this logic in the main method to reverse the string.
Initially, you can start by taking strings where all characters have the same typecase. Gradually, you can challenge yourself by adding symbols, punctuation marks, and, different typecases.
// for I/O operations
import java.util.Scanner;
public class StringReversalClass {
public static String ReverseString(String str) {
// create a new string here using StringBuilder
StringBuilder sb = new StringBuilder();
for (int i = str.length() - 1; i >= 0; i--) {
sb.append(str.charAt(i));
}
return sb.toString();
}
// main function
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter the string that you want to reverse: ");
String original = scanner.nextLine();
String reversed = ReverseString(original);
System.out.println("Original String: " + original);
System.out.println("Reversed String: " + reversed);
}
}
Initially, you can start by taking strings where all characters have the same typecase. Gradually, you can challenge yourself by adding symbols, punctuation marks, and, different typecases.
2. Check Palindrome
A palindrome is a string that is the same when it is read from forward or backward. In this problem, you need to check whether a given string is a palindrome or not. If it is a palindrome, you can return “true” or “yes”. If not, return “false” or “no.”
For example, if the string provided is “level”, it is read the same way from both sides. Therefore, your output will say that the string is a palindrome. In case the string is “CodingZap,” since it is not a palindrome, your program should return that the string is not a palindrome.
Have a look at the program given below. This could be one of the ways to check if the string is a palindrome or not.
import java.util.Scanner;
class Palindrome {
public static boolean isPalindrome(String str) {
// if the string is empty, it is a palindrome
if (str == null || str.isEmpty()) {
return true;
}
// converting the string to lower case
//str = str.toLowerCase();
int left = 0;
int right = str.length() - 1;
while (left < right) {
char leftChar = str.charAt(left);
char rightChar = str.charAt(right);
// Check if characters are equal
if (Character.toLowerCase(leftChar) != Character.toLowerCase(rightChar)) {
return false;
}
left++;
right--;
}
return true;
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a string: ");
String str = scanner.nextLine();
if (isPalindrome(str)) {
System.out.println(str + " is a palindrome.");
} else {
System.out.println(str + " is not a palindrome.");
}
scanner.close(); // Close the Scanner to avoid resource leaks
}
}
Let us see the output below. Here we have taken ‘Racecar’ as the input string. This string is a palindrome. Therefore, our output returns the same.
Output:
3. Find The First Unique Character
The next exercise you can practice is to find and output the first non-repeating or unique character in a string. You can do this by creating a function in Java programming language.
For example, if the string is “Google,” we can see that the first character that does not repeat itself here is ‘l.’ Thus, our output for this case will be ‘l.’ Let us see this in the code example below.
// For I/O operations in the code
import java.util.Scanner;
public class FindFirstUniqueChar {
public static char findUniqueChar(String str) {
// using nested loops to compare characters
for (int i = 0; i < str.length(); i++) {
char currentChar = str.charAt(i);
boolean isUnique = true;
// Check if current character appears earlier in the string
for (int j = 0; j < i; j++) {
if (currentChar == str.charAt(j)) {
isUnique = false;
break;
}
}
// Check if current character appears later in the string
for (int j = i + 1; j < str.length(); j++) {
if (currentChar == str.charAt(j)) {
isUnique = false;
break;
}
}
if (isUnique) {
return currentChar;
}
}
// When no unique character is found we will return a blank space
return ' ';
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a string: ");
String str = scanner.nextLine();
// converting the string to lowercase for ease of solving
str = str.toLowerCase();
char uniqueChar = findUniqueChar(str);
if (uniqueChar == ' ') {
System.out.println("No unique character found in the string.");
} else {
System.out.println("First unique character in the string is: " + uniqueChar);
}
}
}
Enhance your code by adding functionalities for handling empty strings or strings with numbers. By practicing this challenge, you can get better at tasks like data processing, where you need to identify unique elements within textual data.
4. Count Vowels and Consonants
Next on our list of Java exercises is the program to find the count of vowels and consonants in a string. How will this work? Let us see below.
Take an example string “codingzap.” Here, you will count vowels and consonants and display them in the output. So, the output for this example would be – vowels: 3, consonants: 6. Let us implement it in a code example.
import java.util.Scanner;
public class CountVowelConsonant {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a string: ");
String str = scanner.nextLine();
int vowelCount = 0;
int consonantCount = 0;
// Convert the string to lowercase to handle case-sensitivity
str = str.toLowerCase();
for (int i = 0; i < str.length(); i++) {
char ch = str.charAt(i);
// Check if character is a vowel or consonant
if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
vowelCount++;
} else if (ch >= 'a' && ch <= 'z') {
consonantCount++;
}
}
System.out.println("Vowels: " + vowelCount + " Consonants: " + consonantCount);
}
}
This Java exercise will help you improve your Java skills in character classification and string iteration tasks. Moreover, you can test your knowledge in loops and character checks by writing code for this exercise.
If you find yourself stuck on debugging issues while solving these challenges, our guide on best Java debugging tips for developers can help streamline your problem-solving process
Array And Collection-Based Challenges In Java for Intermediate Programmers
Besides string, Java programming also has different data types like arrays and collections. An array has a fixed size in Java, collections, on the other hand, can reduce or increase their size as per the requirements.
Many coding interviewers ask questions related to these concepts to applicants. So, let us see how can we practice these exercises.
5. Find The Largest And Smallest Element In The Array
In this exercise, you need to write Java code to find and return the maximum and the minimum number in a given array. After you practice this code, you will also be able to write code for sorting algorithms with ease.
Consider an example array [23, 12, 4, 33, 51, 7] You need to create methods to search the largest and smallest number. Here, these are 51 and 4 respectively. Have a look at one code example below.
import java.util.Scanner;
public class FindLargestSmallest {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter the size of the array: ");
int size = scanner.nextInt();
int[] arr = new int[size];
System.out.println("Enter the elements of the array:");
for (int i = 0; i < size; i++) {
arr[i] = scanner.nextInt();
}
int largest = arr[0];
int smallest = arr[0];
for (int i = 1; i < size; i++) {
if (arr[i] > largest) {
largest = arr[i];
} else if (arr[i] < smallest) {
smallest = arr[i];
}
}
System.out.println("Largest element: " + largest);
System.out.println("Smallest element: " + smallest);
}
}
Keep in mind the concept of time complexity so that you practice how to write optimized code.
6. Remove Duplicates From A Sorted Array
This is one of the Java challenges that can also be solved by a beginner with a strong basic knowledge of Java. So, what is the problem statement for this exercise? Let us understand it below!
Let us suppose you are given an integer n representing the size of an array and also a sorted array arr, for example [ 1,2,3,3,4] Now, you need to create methods or a function that helps to return the value of the length of the array excluding the duplicate values.
public class RemoveDuplicates {
public static int removeDuplicates(int[] arr) {
if (arr.length == 0) {
return 0; // Handle empty array case
}
int unique = 0;
for (int i = 1; i < arr.length; i++) {
// If current element is different from the previous one, it's unique
if (arr[i] != arr[unique]) {
// Move the unique element one step ahead
unique++;
// Copy the current element to the unique position
arr[unique] = arr[i];
}
}
// The new length is the unique + 1
return unique + 1;
}
public static void main(String[] args) {
int[] arr = {1, 2, 3, 3, 4};
int newLength = removeDuplicates(arr);
System.out.println("Original array: ");
for (int num : arr) {
System.out.print(num + " ");
}
System.out.println("\nOriginal length: " + arr.length);
System.out.println("\nLength after removing duplicates: " + newLength);
}
}
In the above code, we are checking a value with its previous one. If it doesn’t match, we are assigning its index to the unique variable and then again running the loop to compare other values.
Here, the initial length was 5. After removing duplicates, the final length that is to be printed is 3. Test yourself by solving this problem in constant memory!
7. Merge Two Sorted Arrays
Practice merging two arrays or lists in Java programming language. It is one of the exercises that will help you in learning and developing coding skills in data structures.
You will be given two different lists that are sorted. Your job is to create methods to join them. The resulting output should also be sorted.
Consider examples of lists: list1 = [1,2,4] and list2 = [1,3] After merging, the result will be [1,1,2,3,4]
8. Armstrong Numbers
Armstrong numbers are those numbers whose sum of cubes is equal to the given number itself. The level of this exercise is from beginner to intermediate. To practice this Java code, you need to create a function that checks if the given number is Armstrong or not.
Consider an example value of input integer to be 153. Now, since 153 = 1^3 + 5^3 + 3^3, we can see it is an Armstrong number. In this case, your function returns true, otherwise, it returns false. This way, you can check Armstrong numbers for other input values as well.
Let us see how to implement it. Have a look at the code below. You can modify it as per the requirement of your solution.
import java.util.Scanner;
class Armstrong {
public static boolean isArmstrongNumber(int num) {
int originalNum = num;
// initializing sum to 0
int sum = 0;
int Digits = String.valueOf(num).length();
while (num > 0) {
int remainder = num % 10;
sum += Math.pow(remainder, Digits); // Calculate power of each digit
num /= 10;
}
return originalNum == sum;
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a number: ");
int number = scanner.nextInt();
if (isArmstrongNumber(number)) {
System.out.println(number + " is an Armstrong number!");
} else {
System.out.println(number + " isn't an Armstrong number!");
}
scanner.close();
}
}
Let’s see the output of this program to see if it works or not. Have a look below.
9. Reverse A Number
Take your Java Skills to the next level and solve the program to reverse a number. It is pretty much like string reversal. What is the method to do it? What do you need to define in the code? Let’s see the problem that we need to solve here.
Let us say that the input number is 5412, reversing it should give the output as 2145. You can challenge yourself to reverse a decimal point number where the decimal remains in the same place. So, the input of 5412.34 will result in 4321.45.
This is one of the practices Java exercises that requires the basic knowledge of loops (for loops or while loops) in Java.
Advanced Challenges Involving Algorithms And Data Structures
It is now like to take Java programming exercises from basics to expert level. While each program we discussed above could be solved with basic knowledge of Java programming language, you need more than just basics to cover the following programming exercises.
Data structures and algorithms are one of the vital concepts in the world of programming and coding. From basic algorithms to nested loops, creating objects and classes, linked lists, and structures like an array, stack, and queue; everything is crucial to know for developing coding skills.
Let us explore more Java exercises that can help us to do so!
10. Java Singleton Class
A singleton class is a design pattern in Java programming language that helps to ensure that a class has only one instance. This instance (object) is provided with a global point of access. To implement this design pattern, you will have to define a singleton class in Java.
In your Java code, you will have to create a non-parameterized private constructor for this class and declare a static instance variable. Here is how you can do it-
public class MySingleton {
private MySingleton() {} // non-parameterized constructor
}
After this, you need to define a static method, getInstance(), to check if the object exists in the class or not. See the code below to know.
private static MySingleton instance;
public static synchronized MySingleton getInstance() {
if (instance == null) {
instance = new MySingleton();
}
return instance;
}
Optionally, you can run test cases to verify if your class is implemented correctly or not.
11. Check For Balanced Java Stack
A stack is a data structure that follows the Last In First Out(LIFO) approach. We say that a stack is balanced when it meets certain criteria. In this Java program, you will explore how to write code to check if the stack is balanced or not.
You will have to create a method that takes the input value as a string and returns true if it is balanced. Otherwise, it returns false. There can be multiple solutions and approaches for this. Find the one that best answers the problem.
12. Binary Search Algorithm In Java
Upgrade your Java skills and test them by implementing the binary search algorithm program. Binary search is performed in a sorted array, so when you input your array, you need to sort it first and then perform the searching task.
It is one of the most frequently asked programs in interviews for Java programming language. Thus, knowing how to write code answers and implementing solutions for such concepts is really helpful to crack computer science interviews.
What Are The Resources For Java Coding Exercises?
The coding world provides you with a lot of resources so that you can develop your skills and progress continuously. Let us see some resources that can help you to learn Java exercises and solve problems.
Have a look at the list of resources below-
Online Coding Platforms- Platforms like HackerRank, LeetCode, and CodeChef are great resources where you can write Java solutions and submit your answers. They are like a data dictionary for thousands of problems in Java that you can solve.
From basic programs like string reversal and loops to implementing advanced-level solutions in object-oriented programming, exception handling, and data structures, you can practice anything and everything here.
Frameworks and dedicated websites to learn Java- There are a lot of websites that are designed specifically for people who wish to learn Java. You can find curated coding challenges from the basic level to the hard level here.
Moreover, these exercises available are curated in such a way that helps students grasp Java concepts and syntax with ease. CodingZap also provides exceptional services in live 1:1 classes in Java. You can explore more on our website.
Tips To Improve Java Skills By Solving Challenges
As we progress in our article, let me now tell you what are some useful tips that can help you improve your coding skills and help you come up with better solutions to Java challenges. Keep reading further to know!
Maintain Daily Streak- By solving at least one coding challenge every day is the key! It is very important to stay consistent while learning Java or any other programming language as you will be then able to get familiar with a new concept and revise old solutions by just giving your few minutes.
Analyse The Problem Statement- Once you understand the problem you solving, whether it is about string, array, or loops, half of the job is complete! Anazyling challenges help you to come up with ideas and help develop logic-building skills.
Engage With Java Community- A great thing about programming platforms is the discussion forums where you can engage in conversations with fellow coders and learn new approaches to writing code for challenges.
Test Your Knowledge- Once you feel confident about the syntax and basic concept test your knowledge by participating in online programming contests or skill-certification tests.
Conclusion:
I hope that by now you have everything you need to know about Java coding challenges. Remember to stay consistent and get a good knowledge of basic Java fundamentals and best practices so that your journey to learn Java goes smoothly.
If you find yourself stuck with Java coding challenges or assignments, our team at CodingZap is here to provide you with one-on-one guidance to level up your Java skills.
Let’s make coding easier for you!
Takeaways:
Practicing programming challenges regularly is an important factor in improving your skills and mastering Java programming.
The best platform to practice Java depends on the concept you want to learn. HackerRank is one of the popular platforms for beginners. LeetCode, on the other hand, is fit for coders who want to practice more complex tasks.
Coding challenges also help you to write optimized code and enforce your learning in the form of practical implementation of real-world scenarios.
