How to create ArrayList from Array in Java
The problem
If you have a traditional array, that looks something like the following:
A[] array = {new A(1), new A(2), new A(3)};
And you would like …
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342 articles about java development, tools, and best practices
How to Remove all Vowels from a String in Java
The challenge
Remove all vowels from the string.
Vowels:
a e i o u
A E I O U
The solution in Java code
Option 1:
public class VowelRemoval {
public …How to Solve Max-Min Arrays in Java
The challenge
You are given an array of unique elements, and your task is to rearrange the values so that the first max value is followed by the first …
Read Article →How to do Basic Encryption in Java
The challenge
The most basic encryption method is to map a char to another char by a certain math rule. Because every char has an ASCII value, we can …
Read Article →How to Find the Squares in Java
The challenge
Complete the function that takes an odd integer (0 < n < 1000000) which is the difference between two consecutive perfect squares, …
How to Get Longest Word in Sentence in Java
The challenge
When given a string of space-separated words, return the word with the longest length.
If there are multiple words with the longest …
Read Article →Maximum Different of Int-Array in Java
The challenge
You must implement a function that returns the difference between the biggest and the smallest value in a list(lst) received as a …
Read Article →Indexed Capitalization in Java
The challenge
Given a string and an array of integers representing indices, capitalize all letters at the given indices.
Example: …
Read Article →How to Spacify a String in Java
The challenge
Modify the spacify function so that it returns the given string with spaces inserted between each character.
spacify("hello …How to Validate Usernames with Regex in Java
The challenge
Write a simple regex to validate a username. Allowed characters are:
- lowercase letters,
- numbers,
- underscore
Length should be between 4 …
Read Article →Sort Lexicographical Order of Substrings in Java
The challenge
Given two arrays of strings a1 and a2 return a sorted array r in lexicographical order of the strings of a1 which are substrings of …
How to Perform Alphabetical Addition in Java
The challenge
Your task is to add up letters to one letter.
The function will be given an array of single-character Strings, each one being a letter …
Read Article →How to Encrypt Words in Java
The challenge
You want to create secret messages which must be deciphered.
Here are the conditions:
- Your message is a string containing space …
How to Fold an Array in Java
The challenge
In this challenge, you have to write a method that folds a given array of integers by the middle x-times.
An example says more than a …
Read Article →Delete Occurrences of an Element if it occurs more than N times in Java
The challenge
Given a list lst and a number N, create a new list that contains each number of lst at most N times without reordering. For example if N …
Read Article →How to Validate Phone Numbers in Java
The challenge
Write a function that accepts a string, and returns true if it is in the form of a phone number.
Assume that any integer from 0-9 in any …
How to Sort Array by Frequency in Java
The challenge
Sort elements in an array by decreasing frequency of elements. If two elements have the same frequency, sort them by increasing value. …
Read Article →How to Calculate String Rotation in Java
The challenge
Write a function that receives two strings and returns n, where n is equal to the number of characters we should shift the first string …
Read Article →Compare Strings by Sum of Chars in Java
The challenge
Compare two strings by comparing the sum of their values (ASCII character code).
- For comparing treat all letters as UpperCase
null …
How to Add Two Integers Without Arithmetic Operator in Java
The challenge
Given two integers a, b, find The sum of them, BUT You are not allowed to use the operators + and –
Notes
- The numbers (a,b) may be …
Counting Method VarArgs in Java
The challenge
Count how many arguments a method is called with.
Examples
args_count(1, 2, 3) -> 3
args_count(1, 2, 3, 10) -> 4
The solution in …
Read Article →How to Sum Consecutives in Java
The challenge
You are given a list/array which contains only integers (positive and negative). Your job is to sum only the numbers that are the same …
Read Article →Replacing Occurences of Words in Java
The challenge
You are given a string. You must replace any occurrence of the sequence coverage by covfefe, however, if you don’t find the word …
Convert String to LeetSpeak in Java
The challenge
Your task is to write a function toLeetSpeak that converts a regular english sentence to Leetspeak.
More about LeetSpeak You can read at …
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