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Questions tagged [java]

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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4answers
366 views

Is Template design pattern a bad practice due to inheritance?

I have been using Template Design pattern in my code for implementing CRUD procedures for different resources. There are some steps which are same for many resources and some which need some addition/...
2
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2answers
212 views

Domain models vs entity models vs Hibernate lazy loading

In a new Java project I plan to use an extra layer above Hibernate entities. So there would be a CustomerEntity and CustomerDomain. The reason for that is that the CustomerDomain can contain extra ...
1
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2answers
77 views

How to allow initial input for a graph of words?

I want to create a java program that can find the shortest word ladder between two words. It's been suggested that I use a graph data structure with words as nodes. The idea being that nodes with ...
0
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1answer
52 views

Generic crud with jdbc api

I am used to programming java on the server side with ORM frameworks and using abstract classes for CRUD. But now I'm workign on a desktop project without ORM and just the good old JDBC API for ...
1
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3answers
193 views

Is it a good idea to use data structures(classes) provided by a dependency in our system?

I am building a new system, which I will call S, that needs to get some data from another system, which I'll name D. System D provides a client and a collection of classes(POJOs) to represent the ...
0
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1answer
65 views

Manage table relationships in Java dynamic web application that accesses a database, without using any framework

I'm developing a web application for academic purposes. What i have to do is a simple website which keeps track of realties along with their respective owners and the tags they are bound to. The ...
1
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2answers
156 views

What do you call a class that can be disabled [closed]

Is there a design pattern that fits this description? A factory that creates classes that can be disabled and enabled. The users of the class don't know if the functionality is enabled or disabled--...
0
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1answer
184 views

Class structure: How should a binary tree and it's node class be implemented in Java in terms of class files?

In implementing a binary tree in Java, should the node class be a separate class file independent of the BinaryTreeclass, or should it be a default class in the same class file as the BinaryTree class?...
5
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3answers
395 views

Java - Does an Interface really have no state or behavior?

going through the web I always read something like Java Interfaces have no state and no behavior If you look what the common definition of state is then you likely end with what the objects ...
2
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3answers
290 views

Is this design with globals bad?

I designed a Snakes and Ladders game. I divided into a reasonable amount of classes and I believe I did a good job regarding the OOP design. I have one question about a decision I made for the design,...
2
votes
2answers
182 views

destroy object once it won't be used anymore in flyweight pattern

I want to use flyweight pattern to return the same instance of my object each time. public class ThingFactory { private static final HashMap<UUID, Thing> things = new HashMap<>(); ...
15
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6answers
3k views

How to implement float hashing with approximate equality

Let's say we have the following Python class (the problem exists in Java just the same with equals and hashCode) class Temperature: def __init__(self, degrees): self.degrees = degrees ...
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0answers
50 views

Two JPA read/write Entities vs SpringJdbcTemplate for implementing CQRS without event sourcing?

So we are trying to implement DDD and CQRS (without event sourcing). I am need of clarity about the implementation details (Spring + JPA). DDD with multiple small aggregate roots require @Entity ...
0
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4answers
187 views

methods that has only behavior and not manage class state, is that violation of encapsulation

This is a simple scenario in an office with employees and their manager. In this scenario, both managers and employees have a name attribute. Only the manager can change his own name Only the ...
0
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2answers
71 views

What to test when testing an API? [closed]

When testing an API (with, for example, Java), what parts should I actually be testing when calling methods of my Controller class (e.g. a Spring RestController)? For example, lets say I've got a ...
1
vote
1answer
114 views

Why doesn't Comparable<T> include any type bound? [closed]

Why do you think the definition of Comparable<T> lacks an upper bound on T? That is, why is it not defined as: Comparable<T extends Comparable<?>> or Comparable<T extends ...
2
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0answers
65 views

Design Pattern to unify similar generated classes

I have a project where I work with generated classes for some web interfaces. Some of these classes are (almost) identical and most of the functionality I need them for only use the identical parts. ...
1
vote
1answer
64 views

Should I place constants related to reading a specific type of file in the FileReader class or in a separate class?

I am writing a class FileFoodReader (in java if that matters) that reads input from a file containing information about foods and their nutritional values. The file has to fulfill some requirements ...
5
votes
1answer
224 views

Why are the instance variables are declared as private in immutable pattern?

As the title says , Why are the instance variables are declared as private in immutable pattern ? I think that the keyword final is enough to avoid any changes that can be done to the value of the ...
1
vote
2answers
112 views

Object Oriented Approach to Calculations

I need to determine the average miles per hour for a trip and an object containing a list of trips. I'm thinking of two approaches. First approach, have a MphCalculator class that I would inject into ...
1
vote
1answer
224 views

Should an abstract class implement an interface, as opposed to defining its own abstract methods?

I'm defining a class structure for persisting to our cassandra database, and I'm unsure about using a combination of an abstract class and an interface. I have two concrete classes, one for persisting ...
3
votes
4answers
977 views

Should a class provide public mutators for all its private fields?

I work on refactoring an Java application based on a CAST audit. One of the criterion says that To respect OO encapsulation concepts, private fields should always be accessed through accessors ...
0
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0answers
364 views

dealing with too many DTO / Java

We are building an pseudo-rest API (because no body cares/funds for a full blown rest API for internal use - which is OK). So we have elements of Rest API (links for resources, API naming conventions ...
0
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0answers
32 views

How can I create a spring-boot application which can be easily extended with plugins?

I am planning a spring boot application that can be extended with plugins. However, I haven't found out yet whether spring boot meets my requirements in this regard. I imagine the following folder ...
0
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2answers
83 views

How to separate responsibilities of a shared entity

Suppose I have game achievement class that stores achievement information like name, popup message, etc. class GoldMedal implements GameAchievement { @Override String getName() { ... } @...
0
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0answers
29 views

JSON-RPC Json Objects Best Practices

I am building a JSON-RPC over UDP socket API in Java. There are 6 objects that will be transmitted in JSON: jsonRequest jsonSuccessResponse jsonError jsonErrorResponse jsonNotification ...
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0answers
54 views

Actor Model In Java Using CompletableFuture and Executors

I am planning to implement an Event Driven system, based on the Actor model using CompletableFutures and individual Thread Pools for each actor. However my tasks are completely sequential in nature ...
1
vote
1answer
146 views

Should I use accessors or public static fields for global constants?

I have to work on some code that was CAST-audited. The report says that it is bad in Java to use public static and that accessors should be preferred. That is also what I was taught at school. The ...
0
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2answers
179 views

Java - difference between constructor and calling the object multiple times [duplicate]

I read through a code example on github and instead of initializing the object using a constructor, they made every setter return the object itself to call it over and over again See, constructors ...
0
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2answers
181 views

What is the difference between singleton pattern using inner static “Holder” class and “Instance” variable

I have encountered two patterns to make a singleton class Holder class public class Singleton { private static final class Holder { private static final Singleton INSTANCE = new Singleton(...
2
votes
1answer
124 views

Law of Demeter helper utilities

Do helper utilities like the one below violate the spirit of the Law of Demeter? It doesn't technically violate the law, since the doOperate method doesn't invoke C's methods itself. If so is there a ...
2
votes
2answers
262 views

Java: Is reflection bad for AOP situations?

Imagine the following situation: 1. Consume a 3rd party WSDL, out comes thousands of classes. 2. There's an opportunity to optimize performance by using a custom paralleled implementation. 3. Wsdl ...
3
votes
1answer
128 views

Automated Testing: where do I put Selenium?

I'm working on a Java application, it's a middleware between two ticketing webapps. I want to write end2end tests using Selenium to test functionality. Let's say my testing process goes like this: I ...
1
vote
1answer
340 views

Why is this valid boolean b = new A() {} instanceof A; if A is an abstract class? [closed]

I have trouble understanding why this boolean b = new A() {} instanceof A; is a valid statement and not boolean b = new A() instanceof A; and why the former is true knowing that A is an abstract class....
3
votes
6answers
275 views

The ID of an object is null at start. Does that make the object state invalid and violate encapsulation?

This question is related to How should an `Employee` class be designed? In the above question, to uniquely identify an employee, each Employee object has an id field as shown below class Employee { ...
1
vote
2answers
213 views

What are the bottlenecks for the Java build speed?

Which underlying system parameters have most influence on how fast a typical Java project (say dozens of classes and dependencies) builds? There is a lot information on JIT (bytecode to CPU ...
2
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0answers
43 views

How to manage cart details across various devices

Recently I was asked in a interview to implement to e-commerce site . One of the requirement was to maintain cart details across various devices .(i.e) if user adds a book from his iPhone , and when ...
1
vote
3answers
109 views

Is there a viable methodology for using a relational database without an Object-Relational Mapping tool

I'm beginning a small Web development project (maybe 20 tables initially). I would like to use a relational database for transactions, SQL, indexes, etc. I have limited needs for true objects, though. ...
0
votes
1answer
93 views

Common methods for swapping out a library

I am trying to come up with a solution to replace joda-time with java 8 time in our product. The code-base encompasses many projects of which some import joda-time directly and some transitively. To ...
0
votes
1answer
348 views

Injecting DAO dependencies into Service Class in Core Java

We don't have any frameworj like Spring where we can inject dependencies using annotations or xml file. We have handler classes, service classes and dao classes. Handler classes access service which ...
0
votes
1answer
255 views

Composite DTO or flattened DTO?

I'm having problem deciding which of these 2 structures to use from my DTOs: Option 1 is: @Data class Lines{ private final Line[] lines; } @Data class Line{ private final String[] specifiers; ...
2
votes
2answers
96 views

API Race conditions

I have an API in which we expect a emailID and a certain deal data. The case is we want to keep the dealId and contactId(email) to be unique. Creating a deal requires data insertion in multiple ...
-2
votes
2answers
64 views

Backtracking with big inputs

I'm doing a Magic Square problem, and I'm using backtracking tecnique for do it. So, the magic square asks you for an input which is the size of the square, and you generate this square, and you need ...
6
votes
1answer
251 views

What is the best way to handle glue between different classicly OOP objects at the higher levels of abstraction?

In object oriented programming, it is commonly said that each class/object/instance should have a well-defined purpose. For example, there may be a Window class in a windowing toolkit, a ChunkLoader ...
2
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0answers
72 views

Third-party API wrapper in Java: how to design

Suppose, there's a site that provides an API, such as this: Users post questions, answers on that site You can make GET and POST calls There are two types of authentication: weak (only gives read ...
2
votes
2answers
297 views

Java 8 - When should I use java.util.Stream instead of java.util.Collection?

I started studying functional programming with JavaScript. After this, I started to study it with Java 8 (streams, lambdas and method reference) and I realised that I tend to use streams as much as ...
2
votes
1answer
482 views

Why did Java and C sharply dip in popularity around 2017 in the TIOBE index? [closed]

The TIOBE Programming Community Index shows Java and C dramatically falling in popularity between late 2016 and mid 2017 before rebounding by mid 2018. What is the cause of the volatility? Source: ...
-1
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2answers
184 views

Java Constructor Syntax and Design [closed]

With regards to object-oriented Java constructor syntax and design, specifically parameterized or specific constructors, it is the accepted process, as describe in books, to build a parameterized ...
0
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2answers
388 views

Is using Objects.requireNonNull() in production bad practice?

Objects.requireNonNull is a helpful method to spot NullPointerExceptions effectively while developing. But in fact it's throwing a RuntimeException which could crash the application (the worst thing ...
7
votes
4answers
618 views

Advantages of HATEOAS based RESTful service

There is a scenario, where we have two commercial applications that are so called REST based(java) but not HATEOAS compliant. Development activity is out-sourced to vendor Development phase of ...