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
- 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 …