Questions tagged [java]
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 bytecode and run in a virtual machine (JVM) enabling a "write once, run anywhere" (WORA) methodology.
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Creating Worst-Case Scenario for QuickSort using Middle Pivot in Java
I've implemented a solution to generate the worst-case scenario for QuickSort using the middle pivot strategy in Java. The goal is to rearrange an input array to produce the worst performance during ...
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FieldInspector: an API for deep object comparison and null checking
Here's my FieldInspector. It compares objects by field values and performs deep null checking. What do you think? It works, but I'm not happy with how it looks. I ...
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Positioning boxes in a box with backtracking in Java
A large cube-shaped box has the dimensions 5x5x5. This box is to be completely filled with smaller boxes. Possible candidates are:
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Handling exceptions of FileInputStream and XSSFWorkbook
Can you tear my code apart with code review comments?
Below is a simple method which reads an XLSX file and does some stuff with it.
I use FileInputStream and ...
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Simple service that wraps access to json file
I'm wondering if this is the best way to write the Java code I have written. It works, but looks overly verbose, is it possible to rewrite any of the code to make it more concise? Please ignore the ...
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Sequentially bidirectional find the indexes of an element into a collection (second thought)
Embodying the helpful tips from the “Sequentially find the indexes of an element into a collection” previous code review resulted in extending the implementation to bidirectional index lookup, that is ...
user277722
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Print the three most occurring chars in Java using streams
The three characters that occurs most in a given string should be printed by using streams/lambdas (functional programming). The order of characters that occur equally often should be preserved.
My ...
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Sequentially find the indexes of an element into a collection
Util class to find into a collection the indexes of a given element with multiple occurrences from the first index or relative to a given index.
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user277679
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Determine top t values with few calls to order(), a given procedure to order k values
Trying to write a decent answer to Most efficient way to get the largest 3 elements of an array using no comparisons but a procedure for ordering 5 elements descendantly, I came up with something ugly....
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Adhering to Object-Oriented Principles in Fruits and Vegetables Scale Program
I've been working on a project related to a fruit and vegetable scale program for about a month, and I'm relatively new to programming. In this project, I'm trying to adhere to object-oriented ...
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Another ATMs cash-out (denomination) algorithm in Java
Related to this question and this answer, I would like to have a second review from you on a modified version.
The problem I tried to solve
Some kind of "Minimum count of numbers required from ...
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Another cash machine with special bill values in Java
Task:
An ATM dispenses banknotes with the following values/denominations: {5, 30, 35, 40, 150, 200}. The user should be able to repeatedly enter an amount divisible by 5 without leaving a remainder. ...
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Is this how you do Spring Cloud Gateway?
I'm new to Spring's reactive Gateway. Here's the code that other collaborator and I wrote (the enum is one of my ideas):
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Implementing an improved merge sort that uses insertion sort, with "levels" - Would this work correctly?
We were asked to improve the merge sort algorithm by introducing insertion sort to the code. We have been tasked with doing this by utilising a "levels" logic. Here is the exact description ...
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"2048" game in JavaFX
I wrote my first code in Java and I need constructive criticism and code review.
This is an implementation of the well-known "2048" sliding-blocks game.
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Determine if it is EU summer time in Java
I wanted to write a utility method for learning purposes to determine if a given date (year, month and day) falls within EU summer time or not, without using any of the Java library methods. Is here ...
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Interview task model implementation(Event Source Java)
I've got a task to implement simple event source and i did: project
Events structure
...
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About self validated Java POJOs
I am currently experimenting with self validating Java beans in order to avoid the creation of objects with invalid states, while keeping the validation knowledge inside the bean. The goals I have in ...
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Reduce time complexity to process sub-arrays
For a given integer array of size n, find all possible sub arrays of size k which range from 1 to n.
Now find the common item which is also a minimum in all sub-arrays of size k, if no common item is ...
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Shrink an array of double elements (uniformly)
Is there a way to avoid the first loop in the method shrink? (if and while...)
The utility ...
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Program using java.io that shows the content of a text file and every three lines the program stop reading, waiting to press Enter
I am doing a program in Java your text using java.io that shows the content of a text file and every three lines the program stop reading, waiting to press Enter. I dont know so much about programming,...
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Improvements for Java Code of a Fruit and Vegetable Management Application
I have developed a Java application as per a specific assignment, which includes features for adding, searching, and removing fruit and vegetable products. I would like a review of my code in terms of ...
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One or more planets to line up with the earth a certain amount of times
I have attempted the below question, however my solution is too slow (i.e. It does not fit the 2 second time constrain for java). How can the solution be optimised?
While at IOI 2020 in Singapore, ...
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Thread-safe coordinate holder
I have been given a task to create a thread-safe RobotCluster class. The idea is that there's a set of robots operating on multiple threads and they each submit the ...
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Verification job with multiple type of batch verifiers
I have a use case where a verification batch job (non-generic) verifies domains based on its input e.g domain_type, batch_pointer etc. The verification handles it based on the domain type which uses ...
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Business logic verification template
I have a use case of template design pattern with generics as mentioned below.
I have AbstractVerificationHandler that provides template for verification business ...
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Add offset to all filenames
From all the files in a directory, the method shiftFilenamesOffset is to increment the numeric part (int) of the alphanumeric filename by offset each time, and ...
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Performance of this BCrypt lossless compressor
The following code compresses a 60-byte BCrypt MCF into 40 bytes.
Does anyone see room for performance or other optimizations?
For example, I should replace Guava's ...
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Find character at given index in a sorted sub strings [closed]
For a given string say dbac the possible substrings are [d,db,dba,dbac,b,ba,bac,a,ac,c]. Sort them and concatenate to a string: ...
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Java Tic-Tac-Toe Game Implementation - Seeking Feedback and Best Practices
I have recently developed a Java program for a simple Tic-Tac-Toe game and would like to request a code review to improve its quality and learn from experienced developers. Below is the code for my ...
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A Java program interfacing with Gnuplot for generating triangle wave plots
Intro
I have this repository.
Given this command
...
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Mapping composition in Java - v2
This post is the continuation of Mapping composition in Java.
This time, I:
Disallowed the null values as the range value.
Simplified the ...
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Spring Boot REST API for moving toy robot in 5*5 grid [closed]
I have designed and coded REST APIs to move the toy robot in 5*5 grid. Please let me know any feedback on improvements, etc
Complete Code here:
https://github.com/pkkht/RobotRESTApp
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Spring Boot Azure Service Bus Listener
I would greatly appreciate your feedback and review of our Spring Boot Azure Service Bus listener implementation. Your insights and suggestions will help us ensure its efficiency and reliability. ...
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Counting duplicate elements in two sorted arrays
I've been working on an assignment that involves optimizing a duplicate finding algorithm for sorted arrays, and I'd like to get your thoughts on the implementation. Here's the code I've come up with:
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Chain of Responsibility in the game of Hangman
I tried to do the Hangman Refactoring Kata for the piece of code over here - https://www.youtube.com/watch?v=-0MeoFTj6DU
This is how the initial code looks like after first set of refactorings (i.e. ...
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DDD Aggregate for seat booking in cinema - is my model correct?
I created a DDD aggregate for booking seats in cinema. Is it corect or it should be model in other way?
Business rules:
1.Seat can be booked at least 1h before screening
2.Screening can has only 1 ...
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blog RESTFUL api with posts and comments
I built RESTFUL api for a blog using java and spring boot(without a frontend).
What it does
the code manages all the http methods on a post inside the blog and comments on that post.
the post consists ...
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Mapping composition in Java
(See also the continuation of this post.)
This time, I have a mapping type:
com.github.coderodde.mapping.Mapping.java:
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Beat Box: an app for making, playing, saving, and loading beat patterns
I was reading Head First Java. The book featured a project called BeatBox that allowed you to make, play, save, and load beat patterns using Java's Sequencer API ...
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Non-recursive topological ordering, starting from given nodes, for Guava graphs
This method returns the topological ordering of a Guava graph starting from a given set of nodes. It's from my personal project github.com/jbduncan/guava-graph-utils, where I'm exploring utilities for ...
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Finance Manager with Embedded Database
I made an CRUD application in Java with JavaFX, H2 Embedded Database and Maven. Can you review my code quickly? Is it well written? What should I improve on it? I don't know if my code is written ...
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A JavaFX program to find out the mouse refresh rate v3
(This post is the continuation of A JavaFX program to find out the mouse refresh rate v2.)
After taking @J_H's suggestions into account, I ended up here:
...
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A JavaFX program to find out the mouse refresh rate v2
(See the continuation of this post in A JavaFX program to find out the mouse refresh rate v3.)
(This post is a continuation of A JavaFX program to find out the mouse refresh rate.)
After adopting the ...
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is my code protected against SQL injections?
im using spring boot and CrudRepository for my queries, the project is about posting content on a blog, so I have a post record with id, creator name, post name, the content itself likes and dislikes:
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FlashCard app using javax.swing
I made a simple flash card app. The general idea is from Head First Java, but it's one app instead of two (for both making cards and playing them) and the implementation is different. What do you ...
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A JavaFX program to find out the mouse refresh rate
(See the next version here.)
Intro
I have this tiny JavaFX program that shows a 800x600 pixel canvas. You are supposed to drag the mouse within the canvas. When you are done dragging, the program will ...
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Distributed lock system using AWS S3
I need a distributed lock system for a service I'm writing. (There can be multiple instances of this service running at a time, and I need to make sure that only one instance does a particular cron ...
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Implement saga pattern with Kafka
There are very few example on how to implement saga pattern with Kafka so I tried to come up with my own implementation choreography saga pattern using Kafka. I need to implement outbox pattern as ...
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Simple vocabulary trainer based on flashcards
Motivation
When I was young, I had to learn english in school and I was really bad. My father told me to write words on little cards, with a word on the one side and its foreign counterpart on the ...
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