Java (not to be confused with JavaScript) is a class-based, object-oriented, strongly typed, reflective language and run-time environment (JRE). Java programs are compiled to byte-code and run in a virtual machine (JVM) enabling a "write once, run anywhere" (WORA) methodology.

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3
votes
2answers
53 views

Determine if a function is bijective

Concise Problem Specification Given an integer \$n\$ and a function \$f : X \to X \$ where \$X = \{1,2,3,..,n\}\$ Determine whether the given function is a bijective function or not. Definition: ...
2
votes
0answers
17 views

Inserting data into a file

So, given a file with the following format: [header] line of data line of data line of data line of data [header 2] line of data line of data line of data ... I add a ...
-3
votes
0answers
18 views

Generate random sequence except prohibited one [on hold]

I need to generate random sequence, but problem is that one sequence is prohibited. I wonder how can I do this code that it will generate correct code in 100% of the cases. This one is still can fail ...
0
votes
0answers
28 views

Time limit exceeded for solving longest palindromic substring by dynamic programming

I have seen plenty of longest common substring search code by dynamic programming and it is an O(n^2) operation. My motivation is to solve leetcode problem longest-palindromic-substring by this ...
2
votes
3answers
103 views

Pattern printing with Name

Found this problem somewhere online and wanted to try this out with my beginner skills. I was able to solve this problem but how can I make my code better? We need to print a pattern like this (each ...
-3
votes
0answers
29 views

Completing a chess move and setting the initial Location of chess pieces [on hold]

I am currently developing a beginner 2-player chess game with java Netbeans. I have a class PieceMovement, which works on the movement of Pieces. In this there is a MoveDone() method, which completes ...
3
votes
1answer
109 views

Find items that appear the same number of times in two collections

Here is a Java collection puzzle I found online. I was wondering if anyone can provide me with suggestions on how Appearance and tests can be improved. Suggestions ...
3
votes
0answers
19 views

Progresses a text adventure by user input [on hold]

I'm coding a text adventure and I'm trying to have both unique and general inputs. The style I'm currently using looks like: ...
0
votes
0answers
18 views

Glueing Java collections into a heap

I have implemented this heap (priority queue) data structure using java.util.TreeMap and java.util.ArrayDeque. The operations ...
0
votes
2answers
63 views

Java synchronization task

I have the following task: Implement a simple command line Java application for booking bus seats. For simplicity suppose there is only one bus, initially all seats (lets say 50) are free. ...
3
votes
1answer
49 views

Shopping cart program in Java with a text menu

I wrote this program to implement a shopping cart. It supports adding/removing items to the cart, viewing the current order, and completing the checkout process. ...
0
votes
0answers
22 views

Updated version of app which does CRUD on a database table

A while ago I created my first Java application. I tried to follow the MVC pattern. I posted my code for review and with the answers I got I did more research and rewrote my code. I gave every ...
0
votes
1answer
58 views

Implementing movement in a Pacman game

I am making a Pacman Player vs Player game in Java, and I am wondering if I am implementing movement in the game in a good manner. Anything that will reduce the code size or make the program faster is ...
1
vote
1answer
26 views

Documentation for a Minecraft server plugin

I'm working on a minecraft plugin for my Spigot Minecraft server. I have a class which works as expected. I've done my best to hammer every single bug out (famous last words, I know) and am now ...
-4
votes
0answers
17 views

How do I loop a specific piece of code in Java with the Switch Command [on hold]

I want to loop MultipleChoice1 if the answer is not either A or B, hence the case "A" and case "B" but when I try to loop it using: int loop = 2 while( loop < 2) (The other codes) case "A": case ...
3
votes
2answers
88 views

Listing employees whose employee number is divisible by some given number

Here I want to improve the code in addListofEmployees and mainMethod. How can I do so? ...
4
votes
1answer
35 views

Binary-octal-hexadecimal conversion table

I solved this exercise of displaying a table of numbers from 1 to 256 in binary, octal and hexadecimal. I made this program to convert from decimal to binary and took that binary number to convert to ...
2
votes
1answer
29 views

Sorting the array of strings on their lengths in Java , Using Maps, ascending order…

I wrote the java method to answer this question : Write a Program to sort String on their length in Java? Your method should accept an array of String and return a sorted array based upon the length ...
0
votes
1answer
28 views

Square ImageView

This is good practice, to make square image? Side of the square container is equal to its width. ...
1
vote
1answer
41 views

Am I doing cookie authentication right?

So I have to write a little social network for a case study at university. I have done some simple webapps before but nothing that required authentication, login and so on. So I wrote this little ...
-3
votes
1answer
62 views

If my code is propely way of Java programming [on hold]

I'd like to ask question about my programming. I am beginner in Java so I want to know if my code is right. Should I change any habits? I'd be grateful for any advice. This is my working Server code: ...
-1
votes
0answers
36 views

Calculating my shocking monthly electricity costs [on hold]

I've been learning Java for a few months now and have finally tried my first project from scratch. I succeeded partially in some of it, but I'm really confused by some other parts of it. I was hoping ...
1
vote
1answer
60 views

Retrieving location coordinates from SQL database and plotting on a map android Gmaps

I am new to Android development. I am currently working on an Android app that fetches changing location coordinates from a SQL database, and plots on a Map view at regular intervals. But I think this ...
4
votes
2answers
283 views

Guess number game with mines

I've made mine first Java program and it was Guess a number game and got some great code review, so I've decided to first implement that suggestions and to make a game a bit more complex/advanced. So ...
4
votes
2answers
75 views

DB-to-Java value mapper

In my company, I've inherited some Java library that I'm now writing tests to, refactoring and fixing Sonar issues. One particular point that Sonar is complaining about is a big chaining of ...
1
vote
1answer
29 views

Logging in to Android application using Firebase

I currently have an app that uses Firebase for logging users in and I would like to know if I can make this code any better. I currently have 4 files: auth/models/User.java ...
4
votes
1answer
67 views

Comparing three data structures for dealing with probability distributions in Java

Introduction Suppose you are given three elements \$a, b, c\$ with respective weights \$1, 1, 3\$. Now, a probability distribution data structures will return upon request \$a\$ with probability 20%, ...
3
votes
1answer
57 views

Simple singly linked list in Java

The list is pretty simple, here is my code: ILinkedList.java ...
2
votes
2answers
48 views

Simulate the “cd” command of a file system

Write a function that provides change directory (cd) function for an abstract file system. Notes: Root path is '/'. Path separator is '/'. Parent directory is addressable as "..". Directory names ...
1
vote
1answer
55 views

Mini Twitter (in memory, single threaded)

I am new to Java and would like to know whether my program is idiomatic. Please help me write idiomatic, terse code. My solution is functionally correct. Design a simplified version of Twitter ...
-3
votes
0answers
17 views

Created JTextField and JButtons which are very hard to see, how to scale them up? JAVA 4k screen [closed]

I have a program which creates three JButton:s and one JTextField. But when I run it, I can barely see them. I have tried to change the parameters to setPreferredSize and JTextField, but that will not ...
-1
votes
0answers
32 views

How to regroup all data for API Endpoints in one place? [closed]

I would like to have every endpoint with parameters, method and endpoint url in one place, so it is easy when I want to change it. To register an account, it is POST ...
1
vote
1answer
108 views

Winning logic for Tic Tac Toe and OO design

I'm a Java beginner and I've just started learning about GUI. However, I'm not sure about GUI coding conventions and whether I'm getting the object orientation part of it right. I feel like I'm ...
9
votes
1answer
90 views

Naive parallel Sieve of Eratosthenes in Java

My naive version now is too slow. I think setting/accessing concurrent atomic bit is way slower compared to access/modify an array of boolean. Second, the parallel execution only happens on the ...
3
votes
1answer
48 views

Queue Using Stack java implementation

Implemented this solution for the problem. Feedback and review if this can be improved in an way. Appreciate your help. ...
3
votes
1answer
70 views

Conway's Game of Life Java Implementation

Keep state the same if it doesn't fall in the following conditions: Change to 2 if there are exactly 2 ones in the neighbors Change to 3 if there are more than 2 ones in the neighbors It is also ...
9
votes
2answers
165 views
+50

Constant-time string equality check

This is my attempt to answer my own equally named question on SO. In this case, I need a method comparing two strings so that the running time is input independent. ...
1
vote
1answer
126 views

Random iteration over an array using divide and conquer

I have created a utility class which allows random iteration over an array. The idea is pretty much a divide and conquer approach. ...
-4
votes
1answer
51 views

What is a good practice to generate a HTML table from a java class [closed]

I am rewording my earlier question. Below is a code that I am using to generate an HTML table based on some criteria. This is just a sample class, in real we are using a class with complex business ...
-2
votes
0answers
41 views

Dice rolling game [closed]

I created this program and coding for the task mentioned. Could some advice if this is right. ...
2
votes
1answer
34 views

Updating certain values in text file

So I need to update some certain values within text file based on actual values there. Any advice on making it more effective or just readable is appreciated. Example text file: ...
3
votes
1answer
59 views

Printing longest lines

Challenge Write a program which reads a file and outputs a specified number of lines, sorted on length in descending order. Specifications The first argument is a path to a file. The file ...
-3
votes
0answers
27 views

NullPointerException in JavaFX methods [closed]

I am getting null pointer exception when try to use a method in Controller class. I am new in JavaFX, so don't know why its happening. ...
1
vote
1answer
54 views

File Writing optimizations - FileOutputStream vs Writers

I'm using a simple logger on a server, which uses a method that looks like this: ...
0
votes
0answers
17 views

Getting my methods to add grade letter to my array [closed]

I have the code below for a program that using arrays and superclass can calculate the grades of multiple students and take the average and give them the grade letter. I've been going back and forth ...
2
votes
1answer
33 views

DisjointSet with O(1) find and O(1) amortised union

Does this code outperform the common implementation with path-compression and union-by-rank? I'm still okay with a review. GitHub ...
10
votes
3answers
243 views

Finding Pythagorean triplet in array

We have an integer array as: private int[] arr = {1, 3, 5, 14, 18, 29, 78}; We have a function which takes three inputs of the array and checks whether: ...