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.

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Artificial intelligence decision making [closed]

So I am working on a artificial intelligent assistant that is supposed to help you making correct decision when playing the game domino. Basic rules: http://www.pagat.com/tile/wdom/caribbean.html As ...
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0answers
59 views

Having trouble with a for loop evaluating incorrectly [migrated]

I was having this problem today and I'm not sure what causes it. The following code: int totWidth = 19; String header = "Kalle's Numbers"; if (totWidth > header.length()) { for (int j = 0; j ...
2
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2answers
170 views

Java: using final keyword only on method parameters that expect immutable objects? [closed]

I came across the interesting topic about final method parameters and that they essentially don't provide much advantages. I wondered if it would be sensible to mark only those method parameters as ...
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2answers
48 views

Using GNU GPL with classpath exception licensed library in a GNU GPL licensed project

I am working on a project that uses ABCL. License of ABCL is GNU GPL with classpath exception, which means we can link this library with independent modules to produce an executable, regardless of the ...
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2answers
148 views

Is the use of set / get prefix discouraged for methods if they don't actually mutate / access fields

This could be a quirk of the IDE I am using, Android Studio, or it could be something more nuanced that I don't understand. I have a method setCustomFont that appears as a property in the Structure ...
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3answers
161 views

Why different languages have different syntax? [duplicate]

Different programming language always/most of the time use different syntax. For example take PHP, Java and Python. In Php & Java semicolons are compulsory at the end of the line, yet Python ...
2
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2answers
229 views

interpretation of the statement in java

I am confused over the interpretation of the following statement Fruit x= new Fruit(); My interpretation is that the new operator along with Fruit(); creates a new object somewhere in the memory. ...
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1answer
51 views

JEE MVC, controller calls the interface instead of the interface implementation

I'm following this tutorial: http://wiki4.caucho.com/Building_a_simple_listing_in_JSP It creates a basic web application in Eclipse using the MVC pattern with Resin as the web container. Here's the ...
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3answers
180 views

How to use Guice for an effective API Design?

I am creating a base API in JavaSE, which includes modules like MVP architecture, Service & Repository Layer, Event Model to fire events between presenter etc. I am trying to implement all best ...
1
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1answer
102 views

Pattern to share fields in inheritance

I'm trying to figure out the best way to solve a design issue. I have to be able to clone (I'm cloning them to Apache HttpClient) different types of HttpServletRequest (POST, GET...) and then send ...
0
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1answer
24 views

Where to store (data) classes for webservices

So I'm pretty new in my current company and my current task is to create a webservice that sends some serialized java objects from service A to service B using jaxws (webservices). The senior on the ...
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2answers
89 views

guideline on void methods that do not throw exceptions

In our codebase I saw a method that is similar to following: public void doSomething() { try { ... } catch (Exception e) { ... //log something ... } } ...
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2answers
115 views

Efficiently find whether Binary Search Tree is Height Balanced or not?

A binary tree is height balanced if and only if the two subtrees of root are height balanced and the difference between the two subtrees height is at most 1. I implemented a code in java to find ...
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1answer
81 views

Java - Best way to set properties of an object [closed]

I don't know if there is any difference in performance, or its just a matter of choice, but I am a perfectionist like that, and I'd like to know. Lets say you have the object HolySheet. You can set ...
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0answers
35 views

DDD Request Validation Handling

I stuck somewhere that I can't find a solution! There are plenty of validation questions here, but as far as I see, most of them were asking about entity validation. But what about request validation? ...
4
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1answer
123 views

Where to initialize objects

I have an BallEntity class that is part of a game that uses a Entity Component System architecture. This class have 'components' that are like the attributes of that class. I create and initialize ...
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0answers
51 views

Naming a class: Shadowing or Mirroring or something else? [on hold]

The following class basically seeks to maintain a copy of the contents of a JMS Topic. The method onMessage() is called whenever a Messages arrived on a JMS Topic. public class TopicListener { ...
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0answers
62 views

Efficient extensions of degree of separation

I'm trying to play around with the 6 degrees of separation problem, specifically the Kevin Bacon game to find alternative ways of playing the game. I want to eventually port it over to MapReduce, but ...
4
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1answer
107 views

Separate interface for mutation methods

I've been working on refactoring some code, and I think I may have taken the first step down the rabbit hole. I'm writing the example in Java, but I suppose it could be agnostic. I have an interface ...
4
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3answers
133 views

Nested POJOs, exposing collections, detecting changes

I have a couple plain object classes to represent data read from a file. They look something like this: public class Command { private String name; private List<Message> messages; } ...
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2answers
107 views

Find the maximum number of pairs of numbers that are in a range, between two arrays

Lets say I have two arrays A and B A = {1,2,3} B = {12,11,67} and have max sum value S = 10 How many maximum number of unique pairs can be formed between the two arrays who's sum is less than or ...
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2answers
98 views

Naming convention for getting the primitive backing a type?

I have a class that is backed by a double value, and I am wondering about accessor method names that preserve abstraction. Based on my experience in Java, there seems to be at least two precedents: ...
1
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1answer
140 views

How can I make an object/class inaccessible to Reflection

I am building an API for minecraft called the Quantum API. We all know that reflection can be used to do some nasty stuff to classes, and even cause undefined behavior if used without care. Is there ...
3
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2answers
93 views

Does a serializable singleton imply both value and reference semantics at the same time?

I was reading Effective Java, and I came across passages that talk about ways you might implement a serializable singleton, as if this was a perfectly normal thing to do in Java. This immediately ...
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4answers
205 views

Is collection object better being immutable? [closed]

As per this link, it is an advice that: A good object should never change his encapsulated state. Remember, an object is a representative of a real-life entity, and this entity should stay the ...
12
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2answers
448 views

Packaging structure of Java collections (java.util) - why does Iterable sit in java.lang?

As per the below diagram, except for interface Iterable, all the remaining constructs (interface / class / abstract class) sit in same package java.util   Why does Iterable sit in ...
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0answers
34 views

Map-Reduce sorting: before or after partitioning?

At some point, the (key,value) outputs of the mappers are sorted by key.As I understand, this sorting doesnt take place locally on the node of the mapper.So I can think of two possibilites: 1) does ...
2
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2answers
171 views

Has-A or Is-A or some strategy pattern?

I am developing a web based application which is about tracking Fleet units. Actually i have already developed the system but in the last six years things changed a bit. Ordinary the software ...
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0answers
42 views

JavaFX Synchronize DataModel with Business Domain

I am currently working on a javaFX (first time) frontend for one of our applications. For this i'm using a simple MVC pattern where my model classes use properties so that i can directly bind them to ...
11
votes
1answer
339 views

Is it good practice to implement two Java 8 default methods in terms of each other?

I'm designing an interface with two related methods, similar to this: public interface ThingComputer { default Thing computeFirstThing() { return computeAllThings().get(0); } ...
4
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3answers
272 views

Java & REST API: How do I check for duplicate before inserting record?

I am developing an application in Java to parse and upload records from a CSV to an online database, via a REST API. While I know for sure that there are no duplicate records in each CSV file, I ...
0
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2answers
194 views

Why 'class String' definition has 'final' modifier? [duplicate]

This answer gives an indication that class String is declared final for thread safety, which does not convince. This answer does not convince when it says: And so, you make the classes final. There ...
32
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6answers
4k views

What's the point of implementing a Stack using two queues?

I have the following homework question: Implement the stack methods push(x) and pop() using two queues. This seems odd to me because: A Stack is a (LIFO) queue I don't see why you would need ...
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2answers
106 views

Dependency injection of ViewModel with unmanaged parameter

I have a PersonEditViewModel which needs two other objects, the personId and the PersonRepository. PersonRepository is obtained from a service locator: private final int personId; public ...
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3answers
73 views

When is a event listener invoked during program execution?

I am using the Obervable-Observer Pattern. MyClass extends Observable{ invokeListeners(){ doSomething; setChanged(); notifyListeners();//This invokes onUpdate() in "implements ...
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0answers
22 views

WebService NameSpace doubt

I am creating a java webservice. For that I am using @WebService annotation and @WebMethod for defining endpoint and service respectively. In both place I have option to provide targetNameSpace. Can ...
1
vote
1answer
92 views

If the representation part of type abstraction is declared private, then how does sub-classing violate encapsulation?

Here, I learned that sub-classing violates encapsulation: it violates encapsulation, since the implementations of the superclass and subclass become tightly coupled For instance, If we consider ...
0
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1answer
111 views

How to decompose Monolithic applications into Microservices with interdependent functional modules?

I work with a large monolithic web application that has between 12-24 functional modules and these are all maintained inside a single war project structure. While the code itself is already segmented ...
2
votes
1answer
190 views

Difference between Consumer/Producer and Observer/Observable

I am working on the design of an application that consists of three parts: a single thread that watches for certain events happening (file creation, external requests etc.) N worker threads that ...
0
votes
1answer
59 views

Graphs and minimum spanning trees?

I am having a hard time finding information on how Graphs and spanning tree's work and how to construct/structure them. The reason is that I'm using a Delaunay Triangulation algorithm within the ...
1
vote
4answers
100 views

Best way to handle blank dates

I'm trying to create a contact book application, and currently I'm working on a class called Person. One of the fields of person is dateOfBirth, however I don't know how to handle unknown dates. Until ...
3
votes
2answers
141 views

Is it still a good practice to log parameters and returns?

Just a context, I am currently making a base code for a Java Spring Boot Application. I am currently setting up the logging of the application and I stumbled upong this url and found it helpful. ...
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0answers
57 views

What exactly meant exactly by “to sort a stack in ascending order”?

There is an assumption made in solutions to this problem: Sort a stack in ascending order. The non-recursive solution looks like this: public static StackWithMin<Integer> ...
0
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0answers
74 views

MVC architecture with JavaFX

I am working on a rather small Java application for a university project. We are forced to use a pretty strange interpretation of the MVC pattern which says that we should only have one generic ...
4
votes
2answers
362 views

How many threads is too many to maintain a chat server?

I'm writing a chat server and client. For the chat server I have 3 "services" all running on their own threads: ConnectionListener that loops over accept, and adds any new clients to a ...
2
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0answers
138 views

Architecture design for Java servlet that triggers work (for sending push notifications)

I'm designing a push notification server (for pushing notification via APNS and Google servers) and have come up with the following design for a Java based web application server. I would really like ...
0
votes
1answer
95 views

Java Serialization - Variables Visible in Text Editor

When I serialize my class and save it as a custom file extension, some of the variables and imports are visible when you open the file in a text editor. Is there a way to avoid this or is there an ...
1
vote
1answer
195 views

Why would we need to rollback twice before closing in a finally block?

I'm trying to implement the change in database connection closing suggested in this question's answers. More than once, I've come across this block of code at the end of my try blocks: try { ...
1
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3answers
130 views

Can multiple synchronized methods in same object run concurrently

As far as i know when there are multiple synchronized methods(both static and instance) in a class, java allows only one such method to run at a time. But what if a thread acquires lock on an object ...
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0answers
38 views

Class design for Token, TokenType and regex constants

For use in a lexer class a have a class Token which represents a token of a specific type and its value, while the types are defined by the enum TokenType in which every token holds its own regular ...