Credit Card Issuer Checking in Java
The challenge
Given a credit card number we can determine who the issuer/vendor is with a few basic knowns.
Complete the function getIssuer() that …
Java
342 articles about java development, tools, and best practices
Find Count of Most Frequent Item in an Array in Java
The challenge
Complete the function to find the count of the most frequent item of an array. You can assume that input is an array of integers. For an …
Read Article →Return Nth Smallest Element in Java
The challenge
Given an array/list [] of integers, Find the Nth smallest element in this array of integers
Notes
- Array/list size is at least 3 . …
Split String into Parts in Java
The challenge
Split a given string into different strings of equal size.
Example:
Split the below string into other strings of size #3 …Exes and Ohs in Java
The challenge
Check to see if a string has the same amount of ‘x’s and ‘o’s. The method must return a boolean and be case insensitive. The …
Read Article →How to make an arithmetic function in Java
The challenge
Given two numbers and an arithmetic operator (the name of it, as a string), return the result of the two numbers having that operator …
Read Article →Using Apache POI to Get or Create a Sheet in Excel using Java
Apache POI provides a mechanism to work with Excel documents.
However, it has a missing feature when you want to only create a new sheet if one with …
Read Article →How to Resolve Scaling Squared Strings in Java
The challenge
You are given a string of n lines, each substring being n characters long. For example:
s = "abcd\nefgh\nijkl\nmnop"
We will …
Read Article →Determine the Last Digits of N^2 == N in Java
The challenge
Let’s call an integer number N ‘green’ if N² ends with all of the digits of N. Some examples:
5 is green, because 5² = 25 …
How to Map over a List of Lists in Java
The challenge
Write a function which maps a function over the lists in a list:
public static <T,R> R[][] gridMap(Function<T,R> fn, T[][] …How to Differentiate a Polynomial in Java
The challenge
Create a function that differentiates a polynomial for a given value of x.
Your function will receive 2 arguments: a polynomial as a …
Read Article →Find the Sums of Perfect Squares in Java
The challenge
The task is simply stated. Given an integer n (3 < n < 10<sup>9</sup>), find the length of the smallest list of …
[Solved] Error: Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.4.4:repackage (repackage)
If you have come across this error when trying to build and deploy your Spring Boot Maven application then this post will help you!
Error: Failed to …
[Solved] No main manifest attribute Solution for Jar/Maven/Gradle/Spring Boot
You’ve built a Java project and packaged a .jar file.
You are ready to run it outside your IDE, or deploy it somewhere.
When you run it using …
Read Article →How to Make a Spiral in Java
The challenge
Your task, is to create a NxN spiral with a given size.
For example, spiral with size 5 should look like this:
00000 ....0 000.0 0...0 …Read Article →
Find the Longest Common Subsequence in Java
The challenge
from Wikipedia:
The longest common subsequence (LCS) problem is the problem of finding the longest subsequence common to all sequences …
Find First and Last Position of Element in Sorted Array in Java
The challenge
Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.
If target is …
Determine if Number is a Power of Three in Java
The challenge
Given an integer n, return true if it is a power of three. Otherwise, return false.
An integer n is a power of three, if there exists an …
How to Count Binary Substrings in Java
The challenge
Give a string s, count the number of non-empty (contiguous) substrings that have the same number of 0’s and 1’s, and all the …
Array Range between Integers in Java
The challenge
Complete the function that takes two integers (a, b, where a < b) and return an array of all integers between the input parameters, …
Number of Rectangles in a Grid in Java
The challenge
Given a grid of size m x n, calculate the total number of rectangles contained in this rectangle. All integer sizes and positions are …
Read Article →Longest vowel chain in Java
The challenge
The vowel substrings in the word codewarriors are o,e,a,io. The longest of these has a length of 2. Given a lowercase string that has …
Determine Unique String Characters in Java
The challenge
In this challenge, you will be given two strings a and b and your task will be to return the characters that are not common in the two …
Difference of Volumes of Cuboids in Java
The challenge
In this simple exercise, you will create a program that will take two lists of integers, a and b. Each list will consist of 3 positive …