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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Strongly connected component finding based on the guava graph library with Kosaraju

I have been writing a small compiler generator for which I need to solve the strongly connected component problem. As the Guava library contains, to my knowledge, no implementation for that problem, I ...
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94 views

Android component animatable on its height

I'd like to have a code review for a component which is supposed to be animatable on its height. It's supposed to be a transitioning element. I find it quite laggy on my phone. ...
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574 views

Pseudo-parallel depth-first search

I'm writing a small program that generates a file containing an adjancency matrix, it then reads from that file, constructs a graph and does something like a parallel depth-first search (dfs) on it. ...
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0answers
93 views

Mahjong hand completeness checking algorithm

As a summer project, I have been working on a small-scale, console-based version of Mahjong (the Rummy-like hand completion game, and not the solitaire version). While having prior knowledge of the ...
5
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113 views

Java multithreading many readers one writer implementations

I have a shared data object with writer threads and reader threads. Number of threads can read from the shared data at the same time (in the code getmethod), and ...
5
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0answers
1k views

Android audio recording using AudioRecord and ByteBuffer

I'm developing an audio recorder app for android using AudioRecord class to have a low level access to audio samples. ...
5
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0answers
184 views

A Java neural network

I have created a neural network in Java, it contains multiple classes. I have uploaded the documentation for the network here: Doxygen, and the full source can be found on Github. Let me start out by ...
5
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2answers
2k views

Loop for inserting a node into a binary search tree

I am trying to implement binary search tree. One method which I am trying to implement in the most efficient and stylish way is node insertion. I am under the impression that while (true) is a bad ...
5
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0answers
3k views

Java AES-256 GCM file encryption

I wrote my first file encryption program, that encrypts a file with AES-256 GCM and stores IV and salt prepended to the file content, so it's likely that I did something worse than possible. I ...
5
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0answers
121 views

Writing service/network layer for mobile apps

I have an app that gets and posts blog posts to and from a server. Right now I have a network client object which is passed into a service object. The service object is created and called from an ...
5
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3answers
512 views

Organizational Tool GUI with Java Swing (and GridBagLayout)

My first 'large' project is to create an organizational tool. Right now, it's pretty basic, but nevertheless functional in terms of the intent of the current release (v0.3.0). My main question is: '...
5
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0answers
113 views

User role Observable

I have a service with these methods: Observable<User> getUsers(); Observable<Role> getUserRoles(String userId); For each user, I want to get her ...
5
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0answers
14k views

Spring MVC dynamically adding form elements

I made a simple form with an option of adding one text field dynamically on mouse click. And I will be grateful for suggestions on how I may improve the code. ...
5
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0answers
2k views

Implement two level caching using spring's cache abstraction Cache and CacheManager

Details about spring's caching framework are here. When I was reading this link, I thought the composite cache mentioned there was one that used levels of caching based on the order given to the ...
5
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0answers
13k views

Using the same RecyclerView.Adapter with a different ViewHolder

I would use the same RecyclerView.Adapter with two or more different fragments. Every fragment uses a different view items layout so I must use a different ...
4
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0answers
86 views

Is this Java small pubsub memory implementation correct and effective?

We want to provide a simple Redis pub/sub alternative in memory for our software. So we implemented this : ...
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0answers
68 views

Extracting cycles from directed graph with max degree 1 and then performing set cover on cycles

I'm trying to solve P1243E in an efficient manner. The problem in simple words is: Given \$k\$ boxes, \$i\$-th box with \$n_i\$ numbers. All numbers are distinct. We need to select one number from ...
4
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0answers
173 views

RGB to YCbCr conversion in Java

I found a Go language code to do RGB to YCbCr conversion from here! I ported it to Java: ...
4
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0answers
121 views

Data processing program

I'm working on part of a service for data processing. The main idea of the service is to get the input data, process it and return the processed data to another service. Input and output data format ...
4
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1answer
180 views

Initializing an Android activity by reading a CSV file with image IDs, names, and descriptions

I am using Java to create an Android app. I have the main activity read a CSV file, create objects, and then save them into a singleton class so the rest of the activities in the app can access them ...
4
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0answers
293 views

Parallel solutions to N Queens Puzzle

I'm trying to increase the performance of my N Queens Puzzle solution. I'd find some threads on SO already but they don't appear to help me to increase performance. My best solution, however, is a ...
4
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0answers
284 views

Optimizing Graph Algorithms for Floyd Warshall and Johnson Algorithm

I am trying to implement and compare Floyd Warshall and Johnson Algorithm(for Sparse Graphs). I have written the following code which produces correct output values for the all pair shortest paths. ...
4
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0answers
90 views

Biometric data representation in Java

This code represents biometric data averaged over a 1min period, beginning at the given UTC time. Please review my code: ...
4
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0answers
103 views

Algorithm to find connected tiles (percolation)

I wrote a little program in JavaFX which displays a path of neighbouring open tiles going from top to bottom. It should simulate a percolation. The algorithm iterates through the whole grid (every ...
4
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0answers
3k views

Updating the UI without leaking the context after an Android AsyncTask finishes

In the past I always did AsyncTasks as private inner classes. The tutorials I found still recommend this (see here, here, here, and here). However, this has the potential to leak the context. Now ...
4
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1answer
487 views

Creating an image in Excel using the colors from an input image

I'm having some performance issues in this code and need some suggestions on how to improve it. I'm not interested in "general code style" improvements unless they have performance implications. The ...
4
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0answers
7k views

Simple MVC CRUD with JDBC

I would like to review my simple piece of code. I am beginner (I learn java for 1 year) and I would like to find out whether I am on good way. I have created simple MVC CRUD java app "ProductManager"....
4
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0answers
120 views

Instantiating an animal using fluent classes with inheritance

I've spent a couple of weeks implementing a simple text editor. The entire program uses only immutable objects and a functional, fluid programming style. After reading about ways to implement Fluent ...
4
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0answers
106 views

Dynamically creating login screen on Android devices

This has been an experience. I'm well above "hello world" java is not a language I use often when programming and I don't program too much. I find myself a lot on Google.... basically just about for ...
4
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0answers
174 views

SAP BPM API - Fetching ProcessInstance & TaskAbstract

I am using SAP BPM API's to fetch currently running process instance and the task belonging to the running process instance. I have return below method on an EJB Class which does the job, however it ...
4
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0answers
89 views

Simplified Google Maps program

I've been trying to write a simplified Google Maps program. My programming experience is limited. I have come up with a solution but I'm looking to make it more user friendly by splitting it up into ...
4
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0answers
156 views

Simple Brainf_ck IDE in JavaFX 8

I have this simple IDE for playing with Brainf_ck. It has no file functionality; only the code, input and output fields are present, and the "compiler" is integrated. Here is how it looks like: My ...
4
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0answers
1k views

JavaFX Scene Video Capture Utility

2 days ago as I was working on my game I decided I wanted to include some sort of a video showing sneak peaks of the themes and tutorials and such. I then decided to check how to record my scene or ...
4
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0answers
2k views

Integer tree sort in Java

I have this algorithm for sorting integer arrays. Basically, it's a balanced tree sort which creates a tree node for each distinct integer, and in each tree node it maintains a counter counting how ...
4
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0answers
111 views

Hash Based Data Structure in Java for Collision Calculation

I have started a project on my free time were I'm writing a 2D game engine in Java. One of the more challenging and interesting aspects of such a project is collision detection between sprites on the ...
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0answers
3k views

Building a tree structure from pairs of parent-child to retrieve all ancestors of a leaf

I am trying to build a tree similar to this one : 1 / \ 2 3 /|\ 4 5 6 / 7 With that tree, I must be able to get all ancestors for each ...
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0answers
211 views

Wavefront-Reader (.obj) in Java - Part 1

I want to implement a wavefront-reader in Java. Therefore I've created some classes to extract a Vector3f and Vector2f (I use ...
4
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0answers
4k views

Hibernate and the Repository Pattern

I have already asked a question on stackoverflow on how to understand the Reporitory Pattern but I'm still having very big troubles in getting a good design implemented on my server. I'm desperately ...
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0answers
74 views

Advice on modelling with generics in Java

Use Case The third party library that I am working with implements its data model in this fashion. ...
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0answers
90 views

Minimum amount of edges that needs to be traversed to visit all vertices… or something like that

So I have this problem, where I'm given m connections over n vertices. The vertices are labeled ...
4
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0answers
585 views

Exception logger for servlets and JSPs

I hate using unnecessary catch blocks and I like to see my code look beautiful. In most of the cases in my project, which is a web application, I can't declare many ...
4
votes
1answer
109 views

Porting a web-based POS system to Android

I'm currently porting a web-based POS system to Android. The Android version uses NavigationDrawer to navigate between menus. What I need a code review on is my ...
3
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0answers
42 views

java swing super simple calculator mvc

i am trying to learn mvc (model view controller). there are many texts out there explaining what mvc is. but not many explaining how to actually code mvc. i found a bunch of questions here asking ...
3
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0answers
41 views

Controller class for an input dialog

I am learning OOP, concretely Java, by developing a real life business application for aimed for repair shops. I have followed MVC pattern design for GUI elements of my application. I was wondering do ...
3
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0answers
46 views

Playframework Java application, saving user details into Couchbase database

I am creating back-end for a web-application in Play framework with Java, using Couchbase for storage. This class is saving and fetching User details from Couchbase....
3
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0answers
75 views

Making a fast Mandelbrot Fractal viewer

I'm making a Mandelbrot set viewer in JavaFX. It takes a while, like maybe 5 seconds to finish. Here's my code: ...
3
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1answer
103 views

Knuth-Morris-Pratt algorithm in Java Finding substrings in a matrix

Problem Given two matrices: a pattern p and a text t. Write a program that counts the number of occurrences of ...
3
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0answers
39 views

Concurrency control between a non-blocking and a blocking methods

In this program, there is a list of Holders that is managed by a singleton class. Each of the Holders keeps a copy of the ...
3
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0answers
42 views

HTTP Delete,Put,Get,Post REQUEST java-ee RESTful services JPA CDI EJB

I am creating introduction app to java ee and APIs of java ee and i want know if my code is ok (like its working but if it could be done better) and what should i avoid in future ...
3
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1answer
90 views

Ensure difference between sets

An endpoint that my application interacts with allows you to specify which fields are returned in the JSON result. My application will then map the JSON to a POJO using Jackson. Quite often I add more ...