Questions tagged [java8]
Java 8 refers to the version of the Java platform released in March 2014.
73 questions
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1
answer
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Java 8 time - LocalDateTime vs LocalDate and truncatedTo limitation handling
I am new to the Java 8 time package, and am trying to better understand it and make sure that I am making good use of it.
Is there a specific reason that LocalDateTime's truncatedTo(TemporalUnit) ...
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118
votes
3
answers
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What is the name of a function that takes no argument and returns nothing? [closed]
In Java 8's java.util.function package, we have:
Function: Takes one argument, produces one result.
Consumer: Takes one argument, produces nothing.
Supplier: Takes no argument, produces one result.
.....
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2
votes
4
answers
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Is the Java Stream API intended to replace loops?
I mean the question in the sense of: Should the occurrence of simple loops on collections in code in Java 8 and higher be regarded as code smell (except in justified exceptions)?
When it came to Java ...
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1
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2
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Choosing a strategy for representing and handling errors (or more generally status codes) in java 8
I asked this questions on StackOverflow but it's definitely a bit too broad.
Even for this website, although the question is about software design, it might not be enough "focused".
I am ...
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16
votes
1
answer
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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);
}
...
- 3,167
2
votes
2
answers
5k
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Dependency Injection vs Static Dependencies
I am building a wrapper for a library that requires little complex logic. The whole project is 8 builder classes, 4 classes for doing some pre-processing, and a couple visitor classes. Essentially I ...
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1
vote
1
answer
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How to remove unused code from a jar file? [closed]
I have a jar file, for example foo.jar. My code contains a lot of libraries (almost 75 jar dependencies). I am not using anything like maven or gradle, I'm just using pure java with pure jar files as ...
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0
votes
1
answer
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Best practice to create model objects in Java
I have an existing microservice that talks to a Natural Language Processing (NLP) product and fetches around 50 fields.
I need to create domain objects in Java now from these fields.
I read about ...
CommunityBot
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14
votes
1
answer
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Reasons for removal of function types in Java 8
I have been trying to understand why the JDK 8 Lambda Expert Group (EG) decided not to include a new function type into the Java programming language.
Going over the mailing list I found a thread with ...
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50
votes
4
answers
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Why should I use "functional operations" instead of a for loop?
for (Canvas canvas : list) {
}
NetBeans suggests me to use "functional operations":
list.stream().forEach((canvas) -> {
});
But why is this preferred? If anything, it is harder to read and ...
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-1
votes
1
answer
207
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Optimizing methods with multiple if checks on getter values
I have a method where I fetch user input, check if certain values exist, and based on that build my own custom input object that I would use to search in a database. The code for the search method is ...
- 478
-2
votes
1
answer
70
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Initialize some values from an array, write more elegant or efficient
I have tried this piece of code:
String[] latitudesArray = latitudes.split(",");
String[] longitudesArray = longitudes.split(",");
Double startLat = ...
111
votes
5
answers
96k
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Why were default and static methods added to interfaces in Java 8 when we already had abstract classes?
In Java 8, interfaces can contain implemented methods, static methods, and the so-called "default" methods (which the implementing classes do not need to override).
In my (probably naive) view, there ...
- 335
-1
votes
1
answer
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views
How to handle pagination in a stateless application having multiple components involved for the data?
This problem statement is around one UI component, 3 service components. The current design of the application is like:
UI makes request to Service-A to get data
Service-A first makes a call to ...
CommunityBot
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7
votes
2
answers
14k
views
Parse both en_US and en-US as locale in Java
I am writing an API (using Java) that takes locale as a parameter. We want the clients to be able to specify "en-US" or "en_US" as they both seem to be widely used across all languages.
I did go ...
CommunityBot
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-2
votes
1
answer
818
views
Refactoring nested if-else interface method in Java8
I have the below default method in an interface and it seems to be pretty complex because of the many if-else conditions.
default void validate() {
Application application = application().get();
...
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52
votes
7
answers
25k
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Workaround for Java checked exceptions
I appreciate a lot the new Java 8 features about lambdas and default methods interfaces. Yet, I still get bored with checked exceptions. For instance, if I just want to list all the visible fields of ...
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59
votes
3
answers
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Is it an antipattern to use peek() to modify a stream element?
Suppose I have a stream of Things and I want to "enrich" them mid stream, I can use peek() to do this, eg:
streamOfThings.peek(this::thingMutator).forEach(this::someConsumer);
Assume that ...
CommunityBot
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-5
votes
1
answer
144
views
Java version: When to migrate? [closed]
About 4 years ago, where I was working, software was still being developed with Java 7 + Swing.
It took me a couple years, but we could finally migrate to Java 8 + JavaFX, two years after that.
Now ...
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1
vote
0
answers
60
views
how to handle external shared libraries, which we do not want to expose
We have 800-900 services we expose via an ESB. Each service is a web app hosted on Tomcat servers. We have 4 tomcat servers per group of services. Our services are split into 4 groups.
Each service (...
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128
votes
11
answers
91k
views
Why use Optional in Java 8+ instead of traditional null pointer checks?
We have recently moved to Java 8. Now, I see applications flooded with Optional objects.
Before Java 8 (Style 1)
Employee employee = employeeServive.getEmployee();
if(employee!=null){
System....
1
vote
0
answers
49
views
subinterfaces redeclaring abstract methods
Why is it that some abstract methods in interface hierarchies are redeclared as abstract further down?
iterator() for example, abstract in Collection is redeclared in Set and List, and again further ...
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0
votes
3
answers
1k
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Populate values in a map from a series of function calls
I have the following common pattern that I need to use in an application:
Given a list of keys, call a function with a parameter to find values for the keys. The function may return null for a given ...
- 2,071
5
votes
3
answers
3k
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Why would someone use @Native annotations?
link : http://download.java.net/jdk8/docs/api/java/lang/annotation/Native.html
In Java 8, there will be @Native annotations.
Indicates that a field defining a constant value may be referenced from ...
4
votes
4
answers
2k
views
Database agnostic DAO (NoSQL + SQL)
Background
While writing a new component, I m in middle of making a decision of SQL/NOSQL database (Mongo vs Mysql) for my storage layer. As of today, mysql seems to be a perfect fit for my use-case (...
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74
votes
3
answers
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Is there a performance benefit to using the method reference syntax instead of lambda syntax in Java 8?
Do method references skip the overhead of the lambda wrapper? Might they in the future?
According to the Java Tutorial on Method References:
Sometimes... a lambda expression does nothing but call an ...
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69
votes
3
answers
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views
Why are the Java 8 java.time classes missing a getMillis() method?
Java 8 has a whole new library for dates and times in the package java.time which is very welcome thing to anyone who has had to use JodaTime before or hassle with making it's own date processing ...
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3
votes
2
answers
2k
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Are there any problems with using class variables in Java that can be accessed by any method?
So I've been coding in Java for a decent amount of time, but recently, I've started a class that cares about my coding design. In the past, if I had two methods inside a class that needed to edit the ...
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5
votes
1
answer
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Parsing Multiple Files and Their Contents in Java using Multithreading without ExecutorService
I'm learning concurrency in Java and went over the tutorials on Oracle website. While I have understood some of it, a greater portion eludes me. I was thinking of a hypothetical problem (though it may ...
- 472
0
votes
1
answer
189
views
Logging parametrized logs while maintaining readability
I have a LogFormatter class which looks like below
@Sl4j
class LogFormatter {
public static String format(String taskType, String taskId, String message) {
return String....
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0
votes
1
answer
812
views
how to write a task factory in java 8
I have various types of tasks, each task involves the following -
Use an XyzAPIProvider to query and obtain a payload
convert the payload into a list of XyzDTOs (ModelMapper)
convert the list of DTOs ...
- 279
7
votes
1
answer
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Should DTO have same structure as payload?
I have a usecase where I am supposed to store entire payload from a third party API in addition to the DTO, say XYZDto, its translated to.
There are two ways to achieve that -
Translate the payload ...
- 221k
3
votes
1
answer
676
views
Writing decision statement on controller layer
We are developing a REST application based on an MVC architecture.
The service layer is returning Optional<T> where T could be any class.
So on the controller layer there is a conditional ...
- 3,167
0
votes
1
answer
3k
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Usage of For-each loop vs functional operation vs Java8 streams
What are the gains in actual computing speed (verbosity of code being put aside) and for which case would each be recommended for, as a good design pattern?
I would like to know the above in general ...
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0
votes
1
answer
876
views
Design and setup a centralized logging with microservices / docker
I am developing on a a large webapp system that has multiple docker containers. Imagine a webapp but with many external restful services running on different containers. A microservices setup.
I ...
CommunityBot
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4
votes
2
answers
1k
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Java8: why two composition methods: andThen and compose?
As a beginner in both java8 and functional programming, I think I'm missing something when reading about function composition since I cannot find a reason why there are two methods that do this, ...
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6
votes
1
answer
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When should I create my own @FunctionalInterface rather than reuse the interfaces defined in java.util.function?
The functional interfaces in java.util.function cover the vast majority of common strategies one might want to apply, but it's also possible to define your own @FunctionalInterface instead. In cases ...
CommunityBot
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6
votes
1
answer
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The use (or abuse) of Java 8, Mapper function
Recently, we have started to migrate a spring application to java 8. The application is divided into 3 layers, rest controllers, service and the repository layer. Our 'architect' proposed that our ...
- 1,403
-2
votes
1
answer
611
views
Why does Java source code contain so many single-letter variables? [closed]
I have been reading the source code of some Java library classes, specifically CompletableFuture. I noticed that the authors are making extensive use of cryptic (single-letter) variables in the code, ...
CommunityBot
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4
votes
2
answers
5k
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Store conditional expression in database
We have an application that allows users to enter conditionals in the form bound op x op bound2, we store this as a string, and then parse it at runtime to evaluate it.
It is a decent amount of work, ...
CommunityBot
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13
votes
5
answers
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Is "static interface" a good practice?
I've just recently noticed there is an option to have static methods in interfaces. Same as with static fields of interface, there is an interesting behavior: These are not inherited.
I'm unsure it's ...
CommunityBot
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19
votes
1
answer
3k
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Does it make sense to measure conditional coverage for Java 8 code?
I'm wondering whether measuring conditional code coverage by current tools for Java are not obsolete since Java 8 came up. With Java 8's Optional and Stream we can often avoid code branches/loops, ...
20
votes
1
answer
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Passing a Scala function to a Java 8 method
The following Scala code works and can be passed to a Java method expecting a function. Is there a cleaner way to do this? Here's my first pass:
val plusOne = new java.util.function.Function[Int,...
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4
votes
2
answers
826
views
Java Design Philosophy
I was reading through design philosophy of java and this line struck me:
"The VM checks whether the signature of the Java code is valid and would refuse to interpret if any change of the code is ...
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13
votes
1
answer
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How does sorting with java 8 stream work under the hood?
When I call Stream.sort(..) is there a new array of elements created and the stream iterates over the newly created sorted array?
In other words, how Java 8 Stream does sort under the hood?
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11
votes
2
answers
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What's the complexity of Java's string split function?
My string is of type"abacsdsdvvsg" or"a a a a a a a"
And I use String[] stringArray = s.split(""); or String[] stringArray = s.split(" ");
I'm wondering what would be the complexity(in O(string length)...
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3
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Java 8: What does a blank return does in a constructor?
This program run successfully . What is use of blank return in constructor as we know it return this implicitly . Is it is a bug in java or have some use .
class Demo
{
int salary;
Demo()
...
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1
vote
3
answers
2k
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Cyclic dependency in this project design
I have 2 modules (containing multiple classes). Let's call them Module A and Module B. Module B has a dependency on Module A: Module B -> Module A. Now, I have created an utility class C, which A ...
CommunityBot
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0
votes
1
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Reference variable concept (Java)
I'm working my way (slowly, but surely) through a book:
Introduction to Java Programming, 10th edition, Comprehensive, by J. Liang (ISBN10: 0133761312)
It explains the idea of a reference variable ...
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votes
3
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Why does java.time have methods for creating objects instead of just constructors?
In the new java.time package the core classes are using the factory method of instead of a public constructor. Even though I like the cosmetics of the of method I can't see a good reason to not use a ...
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