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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Best approach to a defined datastructure

I have a plain text file with some data that I can't change, so I have to create a datastructure to use in reading the file and with that datastructure do some thousands of interactions. The file ...
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2answers
253 views

What type of structure is this in java?

I was reading the following code listView.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) ...
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1answer
162 views

CopyOnWriteArrayList: Why do we have to make a full copy of source data?

I have a lot of confusion about Java's CopyOnWriteArrayist. I know, when we have a modification on it like update, insert of set, it will lock the whole list, copy out a total copy of the source list, ...
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4answers
391 views

Should all programmers know how to solve algorithms, etc [closed]

I'm 15 and have been programming for about 3-4 years. I mostly program in Java as it was my first language. I would like to be a programmer when I'm older, but I'm not sure about the differences. ...
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1answer
56 views

Java Licenses, GPL, GNU Questions

I would like to ask a few questions about software licenses, with regards to a (Java) program I am making. I am very very new to licenses, so please bear with me. 1. If I produce a Java program using ...
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0answers
37 views

Java API initialization step

I am developing an Android Library which involves both Network and Bluetooth communication. In order to start using the library it must be configured. In other words a request to the backend must be ...
0
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1answer
230 views

Separating UI from logic

I'm trying to develop a little game and for this I'd like to separate the UI from the game logic. So I'm thinking of using an "Animator" class that will be responsible for rendering the objects, but ...
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2answers
162 views

Ensure scheduled event only runs once a day?

In a hobby project of mine, a "smart home" for controlling lights, I'm planning to create a feature which turns off all lights at a given time of day. There are also several other features which runs ...
2
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1answer
88 views

Is there a limitation when using the Bloch's Builder Pattern with mandatory fields?

Background I have a class TextDrawable which draws text on top of a shape. There are a number of properties that can be set while creating a TextDrawable object. Mandatory Properties: Text Shape ...
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1answer
220 views

Best OOP pattern to use for creating a commandline SQL API for a proprietary json based company datastore

We need to create a SQL commandline tool for querying a proprietary json based datastore. I'll be using java. Any suggestions on the primary OOP design pattern I should use for building this API? ...
0
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1answer
87 views

when would you wrap a service object with an interface? [duplicate]

I'm new to UT and some of the best practices and anti-patterns when writing testable code, made me think. I used to wrap any service object with interface. but I see many mocking frameworks can ...
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0answers
54 views

when would you write static method as it avoid a “seam” for testing [duplicate]

when would you write static method. I used to write it in utils classes where all the methods are static and work state-lessly on arguments only. But now I know it blocks from creating a seam in ...
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2answers
212 views

Java Multithreading and CPU cores [closed]

I have a simple question this time. If I write an java application with 4 Threads ( each thread does different work ), what will be the difference between single-core, dual core and quad core cpu ( ...
3
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3answers
322 views

Immutable objects [closed]

Looking at questions such as these If immutable objects are good, why do people keep creating mutable objects? What are the drawbacks of immutable types? At what point do immutable classes become a ...
0
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1answer
155 views

Ensure that a method of a class is called after every method call of the same class, how? [duplicate]

I have twenty small methods (m1, m2, m3, etc..) in a class quite different between each other, and after every method i would like to do some common actions, like increasing some counters and in the ...
2
votes
2answers
189 views

Design - Parser.hasInfo(MyClass) vs MyClass.hasInfo()

I'm working on a document processing system. I feel confident with a Document class which represents each document being processed. The issue: Each Document can have a CoverSheet, and if it does, ...
0
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1answer
49 views

Custom mobile app and custom server app [duplicate]

I have this little bit simple and general question. Let's say I build an android app which requires an online server to communicate with. The thing is that I want to make the communication on my own ( ...
0
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3answers
137 views

At what level of abstraction are data structured created?

I am learning about Linked List and Arrays in my data structures class. We are make them in Java. Are actual data structures designed in Java/C? Or are they made in lower level languages like ...
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3answers
152 views

How can DB and UI agree on default values?

I created a table in a Postgres database. I would like to create a form in a Java application to insert rows into that table. Certain fields have default values. What is the best way for the database ...
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3answers
692 views

Clean Code and Hybrid Objects and Feature Envy

So I recently made some major refactorings to my code. One of the main things I tried to do was split out my classes into data objects and worker objects. This was inspired, among other things, by ...
1
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1answer
97 views

Check word density within a document

Here is the situation: I have a Document(d) and a set of keywords (Set<String> keywords). I like to check the density of each words from set keywords with d. I have few solution but not really ...
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0answers
27 views

Designing Document class for Doc Imaging - optional fields

I'm working on a project that processes many Documents. A Document CAN have a Cover Sheet (if the first page is one) A Document CAN have a Stub (if Document is large) It matters whether or not a ...
2
votes
3answers
554 views

OOD: Java inheritance and access to child methods via casting

I have several classes Parent and Child1 ... Child9 implemented in Java. Parent is an abstract class, containing all the common variables of the child classes (a lot, which is the main reason why I ...
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1answer
167 views

Should I declare the most specific type as return type of method?

Sorry for my English In Android I can put only ArrayList of Parcelable objects in Intent: Intent putParcelableArrayListExtra(String name, ArrayList<? extends Parcelable> value); I can't put ...
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0answers
50 views

Standard for expression of relative dates [duplicate]

I'm looking for some kind of standard way of representing dates or dates ranges (for reporting parameter purposes) using expressions. This expression can represent both absolute and relative dates. ...
3
votes
1answer
340 views

What are the main differences between C++ templates and Java generics? [closed]

I'm a beginning C++ programmer coming from Java. It feels to me that C++ templates and Java generics are actually pretty similar. You use them in pretty much the same occasions and in the same way. ...
0
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1answer
98 views

Where to put JPA annotations? Field, or getter?

version in field: @Column(name = "SAMPLE_STRING") private String sampleString; public String getSampleString(){ return sampleString; } version in getter: private String sampleString; ...
0
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1answer
241 views

Logic based on modified fields of a Hibernate entity

I have a Hibernate entity object MyObject with several attributes and a service MyObjectService containing business logic dealing with MyObject. I also have a view model dealing with user input/output ...
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votes
1answer
506 views

How to compare two different hashset objects with more than 100,000 records

I have two classes class A{ int id; String name; public boolean equals(Object o) { if(o instanceof A) { A a=(A)o; if(a.getId().equals(this.getId())) ...
0
votes
1answer
84 views

Project configs for Java projects

How to store configs for project in Java. In normally case i stored it in 'src/main/resources/' with *.properties. How best approach for storing projects config for development, local, production ...
0
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1answer
205 views

Spring web application deployment infrastructure

I'm interested in hearing out what's out there in terms of tips and tricks on deploying and maintaining a Java web application whilst keeping agile. I'm running solo on a startup project I'd like to ...
3
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4answers
487 views

Is it possible/good idea to reduce chance of crashing by catching Error?

I have a class the implements A which will run a certain method of class B. There is a requirement that this A should never crash when running this operation (which is not possible, right?). To ...
2
votes
3answers
140 views

Why return back or assign to a supertype rather than the implementation type?

I have been doing a lot of reading about polymorphism, inheritance and typing (specifically how it applies to Java). I have seen some interesting examples, but not much explanation as to why. I.e.: ...
0
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1answer
123 views

String sentence consistency when sent over sockets

I am learning socket programming. I have a Java application as my server, and C# for the client. Just sending string lines from one to another. Below I have code snippets showing how I am currently ...
0
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1answer
89 views

Coordinating a complicated data migration process

A project I'm involved in has suffered a change in scope, and before I set about trying to cook up some homegrown solution, I'm wondering if there is something out there -- some framework, for example ...
0
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1answer
272 views

Why overriding a static method does not result in polymorphism in java

Many say that we can not override a static methods. But we can override a static method. The question is, when we override a static method why it does not result in polymorphism ?
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2answers
168 views

Is enum not a class? [closed]

I was just exploring enums. One thought came in my mind- what if a class can extend enum. I understand this is not practical, but what surprises me, is the compiler error given- "The type MyEnum ...
3
votes
4answers
751 views

How to force “program to an interface” without using a java Interface in java 1.6

In java 1.8 they have wonderful new "default interface methods". In 1.6 how close can we come? The goal: keep clients (using code) from being able to tell that a class is not a java interface. If ...
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votes
1answer
116 views

Heap vs Stack Memory in java [closed]

I have some doubt on Heap and stack memory in java.. whether those are memory space or algorithm(procedure) of storing data at run time. Here is the class class HeapStack { String str = ...
0
votes
1answer
123 views

Static methods vs Interface implementation

Here is my problem: I stared to create a e-commerce web sites info collector. So i created a parser for each site. The parser class is state less. got methods like: getItemPrice(WebElement page) ...
0
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4answers
1k views

Why is no default constructor generated if you define an explicit constructor?

class Employee{ String name; int id; //No explicit constructors } Now i can invoke the following statement Employee e1=new Employee(); Now the compiler( i'am not sure about who ...
1
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2answers
67 views

Class template specialization for implementing Automata

I'm implementing classes for simulating and generating different kind of automata. I'd prefer to use the same State and Transition classes for all the automata: NFA, DFA, PDA, etc. For a PDA a ...
6
votes
2answers
619 views

What is the difference between uninitialized object variable and object variable initialized to null in Java

I have the following two object variables Date a; Date b=null; Definitely both 'a' and 'b' are not referring to any objects. Now if I invoke following statement System.out.println(a.toString()); ...
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votes
1answer
99 views

How can I test a method which aggregates data from a database? [closed]

I'm developing the web Java application and come across the following issue: I'm using jUnit 4.5. Suppose that I have a method which aggregates data from a database for the rendering their to a ...
3
votes
1answer
414 views

Accuracy of “calculator algorithms”

I am building a library class that provides functionality for mathematical operations on BigDecimals (and a few on BigIntegers). Now, BigIntegers are quite easy to master and pleasant to use. ...
1
vote
1answer
118 views

Is JBPM the right tool for this? [closed]

We have a utility for monitoring directories and taking actions when files appear in those directories. It's in java and takes the form of a standalone jar which launches several threads when started: ...
0
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3answers
239 views

Java Serialization for long-ish-term storage

I have an application that uses a database of about 15,000 Java objects, which I have to read every time the application starts. Originally I've been using JSON to store the data, but that has a few ...
5
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2answers
634 views

Why does java collections not supply a function for the index of max value?

I have been using Collections.max(list) for many projects, but I occasionally want to find the index of that maximum element. I feel silly writing a function to do this for myself in every program I ...
4
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2answers
231 views

@SuppressWarnings in coding test submission

I am working on a coding test for an employer. It is not a particularly hard question but I am trying to do it as well and technically correctly as possible for obvious reasons. I ran into a problem ...
3
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2answers
592 views

How does the JVM handle an exception thrown by the main method?

I understand exceptions, throwing them, handling them, and propagating them to a method lower in the call stack (i.e. throws). What I don't understand is this: public static void main(String[] args) ...