What is the Java equivalent for LINQ? [closed]

Answer 1

There are many LINQ equivalents for Java, see here for a comparison.

For a typesafe Quaere/LINQ style framework, consider using Querydsl. Querydsl supports JPA/Hibernate, JDO, SQL and Java Collections.

I am the maintainer of Querydsl, so this answer is biased.

Answer 2

Java LINQ to SQL implementation. Provides full language integration and larger feature set compared to .NET LINQ.

Answer 3

There is an alternate solution, Coollection.

Coolection has not pretend to be the new lambda, however we're surrounded by old legacy Java projects where this lib will help. It's really simple to use and extend, covering only the most used actions of iteration over collections, like that:

from(people).where("name", eq("Arthur")).first();
from(people).where("age", lessThan(20)).all();
from(people).where("name", not(contains("Francine"))).all();

Answer 4

Now that Java 8 supports lambdas, it's possible to create Java APIs that closely resemble LINQ.

Jinq is one of these new LINQ-style libraries for Java.

I am the developer of this library. It is based on five years of research on using bytecode analysis to translate Java to database queries. Similar to how C#'s D-LINQ is a query layer that sits on top of the Entity Framework, Jinq is able to act as a query layer sitting on top of JPA or jOOQ. It has support for aggregation, groups, and subqueries. Even Erik Meijer (the creator of LINQ) has acknowledged Jinq.

Answer 5

I tried guava-libraries from google. It has a FluentIterable which I think is close to LINQ. Also see FunctionalExplained.

List<String> parts = new ArrayList<String>();  // add parts to the collection.    
FluentIterable<Integer> partsStartingA = 
    FluentIterable.from(parts).filter(new Predicate<String>() {
        @Override
        public boolean apply(final String input) {
            return input.startsWith("a");
        }
    }).transform(new Function<String, Integer>() {
        @Override
        public Integer apply(final String input) {
            return input.length();
        }
    });

Seems to be an extensive library for Java. Certainly not as succinct as LINQ but looks interesting.

Answer 6

For LINQ (LINQ to Objects), Java 8 will have something equivalent, see Project Lambda.

It has Enumerable's LINQ to Objects extensions like stuffs. But for more complicated LINQ things like Expression and ExpressionTree (these are needed for LINQ to SQL and other LINQ providers if they want provide something optimized and real), there is not any equivalent yet but maybe we will see that in future :)

But I don't think there will be anything like declaratives queries on Java in future.