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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2answers
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MVC like design with interfaces: How to handle basic objects?

I have an (android) application and decided that the presentation layer will get data only through strict interfaces from the controller. I am at the point where some basic objects need to be passed ...
1
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0answers
76 views

Java write to text file from multiple threads

I have a thread which read and insert new lines in same file. I must synchronized that file so that no other thread is not accessing the file at the same time. Here is how i will synchronize a file ...
15
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3answers
1k views

Which version of Java should I use for a desktop application to reach the most users? [closed]

Am I correct to assume that most end users are using an older version than Java 8? Since I do not want to force people to upgrade in order to use my application, should I plan it to use Java 7 or even ...
0
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1answer
57 views

Lock object in base class: private or protected? [closed]

I have a base class that contains some lists, queues, and other fields which determine its state. In the base class I only access these fields within a protected lock object since there could be ...
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3answers
163 views

How to design a solution that needs dynamism using Inheritance [closed]

I have below code/classes/interfaces: An Interface: public interface Animal<A extends Animal<A>>{ void fight(A otherAnimal); } 2.Tiger class which is implementing Animal ...
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1answer
49 views

How is ServletContext created?

When the webapp gets loaded the container will create the ServletContext. There is only one ServletContext per webapp per JVM. The ServletContext object is contained within the ServletConfig ...
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0answers
3 views

Constructor Bug [migrated]

I am trying to make a class that represents an integer with 100 digits. Not so much because I need it, but to learn more about constructors. The constructor takes a String (all numbers) and places ...
-1
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0answers
44 views

How to do frequent deployment / rolling upgrades for a Java app?

We're developing a SaaS app in Java, built with Maven. It runs on Amazon on a (potentially) large number of servers. We'd like to deploy changes every day or two. We have a ton of unit and system ...
1
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1answer
144 views

Problems with OO design for application with pluggable components

I'm trying to refactor an ugly code and make it easly extendable in the future. The application should be nothing else but a series of components that have input(s) and output(s). The components ...
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0answers
24 views

NullPointerException from tring to get seperate RGB components [migrated]

I am trying to get the seperate RGB components from each element in a 2D color array,but it keeps throwing a NullPointerException and I am not sure why. It might be something small that I missed, so ...
0
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1answer
70 views

Return values and exceptions [closed]

I wrote simple function that returns a string depending on which condition is TRUE. Here is my code: private String getMyString() { if(!mStrigMember.isEmpty()) { return mStrigMember; ...
1
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4answers
167 views

What is the proper way for these methods to function?

How can I properly design what a method or function should do? To clarify the question I am going to use an example from a simple (non GUI) hangman game I created. The design is simple, it has a ...
0
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0answers
70 views

Is there any necessity to pass a variable parameter to a method while the variable declared global? [duplicate]

I am writing a class in java of Monte-Carlo algorithm. Here is the written code - public class MonteCarlo { int[][] matrix; public void monteCarlo(List<Node> nodeList) { matrix ...
2
votes
5answers
171 views

Implement multiple separate interfaces or interface hierarchy

I've been refactoring one of my projects recently and ran into a decision I have to make. I have several interfaces: Entity: Something in the game world Actor: An Entity that can perform actions ...
0
votes
3answers
202 views

Why are there no java compiler alternatives to allow new functionality? [closed]

For example, a new java compiler could allow for some breaking backwards compatibility to allow for things like overloading on generic types like: void foo(List<String> arr); void ...
11
votes
2answers
616 views

Java has the JVM, what does C have?

I know that C has a compiler but what determines execution performance? For example in an if else block, what if the code just had all ifs instead of if elses, what determines that all the ifs will ...
2
votes
2answers
211 views

When to use a SortedMap interface?

The rule in programming is to use the most general interface possible. But the difference between Map and SortedMap is more subtle. They compile to the same bytecode [I think] No additional safety ...
1
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2answers
104 views

Caveats of using String.hashCode() on a switch on java < 1.7

There are several cases when I want to switch over a String input. I decided for implementing something like: public Object doStuff(String param) { switch (param.hashCode()) { case 1234546: ...
1
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2answers
148 views

My value checker function needs to return both a boolean and a message

I have a value checking function, something much like a credit card number checking function, that is passed in a string, and needs to check that the value is of the right format. If it's the right ...
9
votes
7answers
2k views

Does Oracle reap economic benefits by maintaining Java? [closed]

It occurred to me that many programming languages such as Python and Javascript are maintained by non-profit foundations. I can see why a foundation would update a free programming language- in order ...
1
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2answers
84 views

Adding Logging to a pre-existing Program

I have a game that I have been writing in java as a hobby for a number of years. I have very sparse logging, just some simple output when something goes really wrong. It's about 25,000 lines of code. ...
4
votes
2answers
186 views

Exception versus return code in DAO pattern

After reading a lot about the abusive use of exceptions in Java and how you should let an exception bubble up through the different layers of an application, I've come to a point where I don't know ...
2
votes
1answer
55 views

Transactions and subresources with JAX-RS

I'm porting an existing application RESTful API to a Java web framework -- I don't actually care which -- but it's proving hard to get the basics right. The core of the problem appears to be getting ...
5
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1answer
154 views

Retry design for high volume

I have a Java system using ActiveMQ for messaging. And the system processes about 400 to 600 transactions a second and we have no issue when everything is running smoothly. The system also got to send ...
0
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1answer
57 views

Pattern for separating UI code from logic in Wicket

I'm using Apache Wicket for developing web apps, I have developed a few for the last year and it has been great; today I was looking at a few pages and most of them look like this: public class ...
1
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0answers
32 views

Enforce coding decision to include or exclude an Enum element in an EnumSet at compile time

I would like to enforce that the elements of a Java Enum are chosen or excluded from an EnumSet at compile time i.e. I am forced to make the decision to put it in the set or not whenever I create a ...
1
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2answers
121 views

Is it a good idea to require passwords in offline applications?

I am developing an application which can install extension modules (plugins, if you will) from APT-style repositories hosted elsewhere. The plugins need not be signed (although the downloads are ...
1
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2answers
146 views

Smells in exception handling: how to separate between public and internal exceptions?

During the development of a small web API, we decided to separate internal exceptions from public exceptions. Public exceptions are HTTP exceptions, that translate into HTTP responses with proper ...
1
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0answers
23 views

do my “dal” and “fileHandler” interfaces overlap?

I want my program to: 1) read some input lines from csv file 2) write the output lines to plain string file 3) read some input from the same file in (2) and compare it to some calculated data. I ...
1
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0answers
101 views

Optimal data structure for binary data/Java

I have several input formats mostly restricted to geotiff and some proprietary binary formats. I import them into my program and then need to export them into various other data formats (also binary) ...
0
votes
1answer
98 views

advantage of having multiple REST web services

I have a application designed using Spring REST service. the application has two REST projects: Web Core Web has html, JavaScript and Java classes (ajax calls this REST). These Java classes in ...
2
votes
2answers
149 views

Does anyone else feel like confused even after they're done studying programming tutorial? [closed]

I am learning core java and I was studying from java trails on oracle website. When I was done learning the Thread trail, still there was a sort of confusion and blurriness at the back of my head. I ...
0
votes
1answer
49 views

Handling DomainExceptions using REST endpoint

Suppose I'm doing some DDD. Now, I have a microservice reflecting a bounded context/a part of a bounded context. Now, suppose there is a REST endpoint: '/somedomainmodel/someaction' My API user is ...
1
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0answers
66 views

How and where to make global function file in jsp sevlet web application

I am making a website in Servlet&JSP. I am looking for good way to make a specific function file from where I can call and declare my common functions. If I made a java file function. Java, so is ...
4
votes
1answer
147 views

What are the reasons for sealing a .jar and how would I verify that?

I have created a sealed jar, but I don't see difference compared to using a non-sealed one. What tests I can perform to verify the jar is sealed? What reason we could have to prefer using a sealed ...
0
votes
1answer
80 views

Possible way to make java class builder more abstract by using interface required keys

I'm looking for a more abstract pattern for builders that handles required fields without the need of writing a validator that checks if all requried fields are set. I like this builder. But is ...
0
votes
1answer
84 views

Is set of libraries called API only if it talks to a system/server?

I have read few articles about API. Can't find the reference now. In some of them, they define API as set of tools, routines and protocols which are helping programmer to build a software with use of ...
0
votes
1answer
73 views

best way to export binary data with additional text attributes to a stream

I would like to create a command line API in a Java application to export a binary blob to stdout. I would additionally like to export certain attributes about the blob, ideally in a non-binary ...
28
votes
8answers
4k views

Is throwing an exception an anti-pattern here?

I just had a discussion over a design choice after a code review. I wonder what your opinions are. There's this Preferences class, which is a bucket for key-value pairs. Null values are legal ...
2
votes
3answers
156 views

What is the difference between a variable and a parameter? [closed]

Its a conceptual question. But I would like to use the right term at the right place. That is why I would like to read some other views on this.
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votes
1answer
94 views

Why java has so many frameworks [closed]

why java has so many frameworks? why core java is not sufficient enough to solve the problem or develop anything? Even if core java is insufficient enough that we need frameworks,why there are ...
-1
votes
1answer
81 views

Servlets and JSP begginer help [closed]

I Just finished learning java fundamentals.It took me three days just to configure Apache tomcat into eclipse.Though I am familiar with eclipse, the whole Apache tomcat Interface looks very Alien to ...
4
votes
1answer
106 views

How would I isolate changes to mutable state if I need to run two queries to get the final result?

I'm working on some code that takes search criteria from a Rest API and uses it to query a remote API to return results. As an exercise, I wanted to try to separate all state changes to one place, as ...
-1
votes
5answers
2k views

Why Java is a factor 2-3 slower than equivalent C++ program? [closed]

I know there is an opinion that programs written in Java and running under JVM as as fast as C++ programs, after introducing just-in-time (JIT). I see many cases when Java is terribly slow for simple ...
0
votes
2answers
101 views

How to write a new annotation that behaves precisely like an existing one?

Here is my use case. Suppose annotations did have inheritance and would automatically inherit the entire behaviour of the base class. Then I would do the following (note the two package statements): ...
0
votes
2answers
248 views

What is the rule for nested loop code?

I am new to programming and currently learning Java from Stanford free learning course. There was this assignment that I had trouble translating my algorithm into code. I feel like I have a ...
1
vote
1answer
60 views

Language support for (syntactic) delegation in Java

Composition over inheritance is an old trend or even accepted state of the art in object oriented programming. It would be even easier to use in Java, if there were language support for delegation. ...
17
votes
7answers
3k views

Why is instance creation the way it is?

I've learned C# over the course of the past six months or so and am now delving into Java. My question is about instance creation (in either language, really) and it's more of: I wonder why they did ...
1
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1answer
93 views

Open closed principle vs abstraction leaking (Java enums)

In Java, an enum is not a plain replacement for a number (like in C/C++), but a family of objects which can have properties. For instance public enum Order { NAME("Ordering by name"), ...
12
votes
4answers
808 views

“Use map instead of class to represent data” -Rich Hickey

In this video by Rich Hickey, the Clojure creator, he advises to use map to represent data instead of using a class to represent it, as done in Java. I don't understand how it can be better, since how ...