Java is a high-level, platform-independent, object-oriented programming language originally developed by Sun Microsystems. Java is currently owned by Oracle, which purchased Sun in 2010.

learn more… | top users | synonyms

3
votes
4answers
245 views

Having multiple main classes in a Java project?

Suppose that I have a Java code base and I want to be able to execute multiple tasks that are based on this same base: Run an embedded Jetty web server. Run a one-time initialization of database ...
2
votes
1answer
121 views

What are the advantages of Observables over an iterable of futures?

I recently came across the ReactiveX pattern for asynchronous data-flows. I studied the information provided there and also watched this talk by a Netflix engineer on how they used Observables to ...
6
votes
5answers
178 views

Modular Objects with conflicting implementations

I am working on a game framework that would allow users to use multiple mods/plugins to add additional features to the game. For the remainder of the post, I'll use the following definitions: mod: ...
-2
votes
0answers
59 views

Create an OS X Executable from a Windows Machine? [migrated]

Okay so I made a small java game and packaged it into an .exe and it works just fine... for Windows users. My friends with Unix based systems can't launch the executable so I'm wondering how can I ...
-2
votes
0answers
71 views

Where will object declared as local variable reside in stack or heap?

In java I have heard that object resides in heap memory and local variables reside in stack. Objects created and referenced in a function is local to function rite? Where will that go to. class ...
1
vote
0answers
71 views

Find fastest connection to a certain point

What i'm trying to implement is a program that is searching for the fastest connection from one station to other at a given time of the day. I have a number of stations n, and a number m of lines ...
0
votes
1answer
62 views

Alert when size of continuous stream of events exceeds 1000

A friend of mine was recently asked this question in an interview. Lets say there is a continuous stream of incoming events E1, E2 each with timestamp of entry associated with them. Write a java ...
2
votes
1answer
167 views

Getting started with machine learning a zero sum game?

I have a simple zero sum, discrete, deterministic, complete information board game. I want to machine learn an evaluation function for an AI agent. Suppose each board state has ~20 identifiable ...
18
votes
5answers
1k views

Why would a type be coupled with its builder?

I've recently deleted a java answer of mine on Code Review, that started like this: private Person(PersonBuilder builder) { Stop. Red flag. A PersonBuilder would build a Person; it knows about ...
-4
votes
2answers
53 views

Cache repository violating the SRP [closed]

interface IRepository { Data getData(); } class BaseRepository implements IRepository { public Data getData() { ... } } class CacheRepository implements IRepository { private final ...
34
votes
5answers
3k views

When should I extend a Java Swing class?

My current understanding of Inheritance implementation is that one should only extend a class if an IS-A relation is present. If the parent class can further have more specific child types with ...
0
votes
1answer
72 views

What is the proper or recommended way to save String[]'s, Array's, ArrayList's and int[]'s to Android?

I've looked up this question many many times but keep seeing different answers, what is the BEST way to save array's? It seems ludicrously infantile that there is no standard or easy way to save ...
1
vote
1answer
94 views

Sharing POJO between different handlers

I am trying to automate Business Process which can be characterized as a pipeline with distinct stages. Pipeline can be perceived as A->B->C, where A,B,C are distinct Business Steps that ...
3
votes
1answer
59 views

Is there use case for implementing a callback if a future is returned?

If I have function which returns a future, is there any reason to also include a callback where the callback is simply called right before the future completes? The only advantage I can think of ...
8
votes
5answers
392 views

Inheritance vs additional property with null value

For classes with optional fields, is it better to use inheritance or a nullable property? Consider this example: class Book { private String name; } class BookWithColor extends Book { private ...
-3
votes
0answers
9 views

need to find the index at p percent of the array length, and return all the values before that index point [migrated]

given an int[] x and a perentage p (0 - 100), find the smallest valued element y of x so that at least percentage p elements of x are less than or equal to y. I have code that sorts the array ...
-2
votes
1answer
137 views

Shouldn't Java method parameters always be final [closed]

Say I have a method that writes a string to a file: public void write(String content, File out) { // writes content to out } If I want to protect the parameters and ensure that they are not ...
0
votes
2answers
79 views

Creating a Vector (physics) Class in Java

I'm trying to create a vector (like in physics) class in Java. I want to support vector addition, dot product, scalar multiplication, etc. So, my question is, is it possible to do this with generics? ...
2
votes
1answer
73 views

How can I find out network latency in rest service

I have two Java applications deployed on tomcat. For inter application communication I provide jar file of application (Java API) to other application and it becomes a method call which is fast. Now ...
4
votes
1answer
103 views

What is the point of calculating these variables this way?

I'm skimming through a very popular game's source code at the moment and I came across these variables inside of this class. public static final BlockPos ORIGIN = new BlockPos(0, 0, 0); private ...
1
vote
1answer
44 views

How to use fields from an object after an exception is thrown and the object can't be fully created

The issue that I have is that I need information from an object that a method returns when it throws an exception. It is a little hard to describe so I have this java pseudo code example. I have a ...
0
votes
1answer
52 views

What kind of data structure should be used to store components in an electrical schematic program?

Is there a specific data structure, object oriented programming methodology, and/or approach for achieving what programs like LT Spice, Altium Designer, and Cadence Virtuoso use to manage ...
2
votes
1answer
58 views

Observer Design Pattern with complicated objects

I am trying to currently get a good grasp on the Observer design pattern, but I am stuck wondering about one specific issue. In the examples I have been able to find of implementation, they are all ...
0
votes
1answer
43 views

UML- Aggregation or Association

Below is the problem for which I have created a UML diagram with Staff as superclass and waiter, manager and hosts as subclasses, I understood other parts, except for the relation between table and ...
0
votes
2answers
61 views

Set data in multi-level objects (may be using Java Reflection)

I want to possibly use Java Reflection to set some data at RunTime. My problem is I can't figure out how do I get sub-classes information and use as a part of reflection. I want to use Reflection to ...
-1
votes
2answers
90 views

How to validate Exception messages? [closed]

My superior asked me to validate each and every input field in the project that includes the Exception messages. So, am I correct in using Exceptional Handler for validating Exception message. ...
27
votes
3answers
5k views

If I implement an Interface, is it called an Inheritance?

If my class implements an interface then can I say that I'm following inheritance? I know that when a class extends another class then it's inheritance.
0
votes
1answer
73 views

NoSQL in Java Enterprise Application

I'm planning a large scale enterprise application that requires reliability and standardization comfort that Java EE provides. At the same time, I'm wondering if I go for Java EE, will I be able to ...
0
votes
1answer
87 views

Are new empty Java marker interfaces created to satisfy an existing method contract a code smell?

Suppose I have a POJO A and some client code that serves it. I have created POJO B, which doesn't have anything in common with A, but I want to use it in the methods that use A, so I decided to create ...
77
votes
6answers
13k views

Why are floats still part of the Java language when doubles are mostly recommended instead?

In every place I've looked, it says that double is superior to float in almost every way. float has been made obsolete by double in Java, so why is it still used? I program a lot with Libgdx, and ...
2
votes
3answers
125 views

Logging an audit trail (Java application)

I'm creating a Java (Spring Boot) application for creating Entities. I've got my @Controller for getting the data from a web front end, I've got my @Service for processing the data, and I've got my ...
0
votes
1answer
70 views

Why is a Spring's HttpClientErrorException an unchecked exception?

Oracle summarises the purpose of unchecked exceptions as: The next question might be: "If it's so good to document a method's API, including the exceptions it can throw, why not specify runtime ...
2
votes
1answer
145 views

Checking preconditions the proper way

I have a class with around 1300 lines and it has many CRUD-like methods that need parameters to be checked, for some of them it's more than just a few rules. For clarity purposes, I am going to use ...
1
vote
0answers
18 views

How do I properly manage EntityManagerFactory and EntityManagers for long running tasks?

We're building a JavaFX application that connects to a remote Oracle database using EclipseLink on one end and a SOAP service on the other end. We're writing long running transactions that will pull ...
0
votes
1answer
80 views

Controller calling multiple services

I have a few layers in my WebApplication: Presentation, Service, DAO, Domain. Services call DAO objects which reads data from a Database/File whatever. I have a Controller that needs to fetch data ...
3
votes
1answer
163 views

Forward Slash vs Back Slash vs File.separator in Java

I've seen some programmers doing the following : File file = new File("folder\\subfolder\\subsubfolder"); And I find it totally wrong because of compatibility issues with a different OS than ...
1
vote
0answers
36 views

Why Does JavaFX's GridPane Attach Properties of the Layout to the Components?

I am currently learning JavaFX and I came across a very strange API for laying out GUI components. It is perhaps best explained by it's javadoc: To use the GridPane, an application needs to set ...
1
vote
2answers
125 views

Designing validation classes

This is a follow-up of this question. I decided to implement what the accepted answer suggests, however, I realized I also needed individual public methods for each member the entity to be validated ...
3
votes
4answers
158 views

How to name an exception where condition is not exceptional

NOTE: This question is about finding a proper name for an exception where the condition for throwing the exception has not actually happened (eg. preventing a StackOverflow by throwing a ...
9
votes
3answers
274 views

OOP design problem. Two kinds of empty Optional

I'm writing a quite simple application that deals with hotel rooms reservation. I've got a problem at one stage. I'm processing a queue of orders. For every order one of the receptionists should ...
3
votes
0answers
85 views

Finger Paint path gets huge over time and slows the app

So I am writing a Finger paint app. I have multiple color which user can select. I save the path and paint information inside an array. ArrayList<PaintPath> arrayPaintPath = new ...
8
votes
2answers
169 views

How to resolve LSP violation based on minimum precondition

I have a class Party that has a constructor that takes a Collection<Foo>. I plan to have two subclasses NpcParty and PlayerParty. All Party instances have an upper limit on the size of the input ...
1
vote
1answer
48 views

Redesigning a builder to make it reusable

Let's say I have a builder class (which by the way is not techinically a builder, but it's not a factory either) to generate different rules for a game: public class RuleBuilder { private Game ...
1
vote
2answers
161 views

Should i implement same interface in derived class?

Is there a difference between public class B implements C public class A extends B implements C and public class B implements C public class A extends B Is it just redundant implementation? ...
20
votes
8answers
5k views

What Style is Better (Instance Variable vs. Return Value) in Java

I often find myself struggling to decide which of these two ways to use when I require to use common data across some methods in my classes. What would be a better choice? In this option, I can ...
6
votes
1answer
96 views

Extracting and generalizing “repeated” methods with similar functionality

Let's say we have a class with many methods that do something different but can be grouped together as one "kind of functionality". For example, adding a configuration o setting rules up. Let's go ...
1
vote
4answers
205 views

Readability & Performance: Is it better to allow the Java garbage collector to clear a datastructure?

I work with large HashMap's and ArrayLists. When not needing them to be in memory any longer, I use myArray.clear(); to free up the memory. When my colleague saw that line, he changed it to myArray ...
1
vote
3answers
96 views

Single exit point meets Java streams

We currently have a sensitive discussion going in the company that touches on a couple of old primary opinion based discussions. Nevertheless, I would like to discuss the case in this forum to ...
5
votes
6answers
332 views

Breaking the contract: throw exception or do nothing?

Let's say we have a list of players in our Event class. And we have a dictionary with the score of each player. We can add a score to a player using the addScore method: public class Event { ...
0
votes
3answers
137 views

Should I check for nulls in setters and similar methods?

I have plenty of setters in my classes, as well as many methods to add an item or a set of items to lists or maps. Should I check for nulls for each one of them, or should I allow ...