What is the Java equivalent for LINQ

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What is Java equivalent for LINQ

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Lambdas are now available within Java 8 in the form of JSR-335 - Lambda Expressions for the JavaTM Programming Language

UPDATE: JDK8 has now been released which contains project lambda. It's worth grabbing a copy of Java 8 in Action currently still MEAP.

Have a read of Brian Goetz articles relating to lambdas for a decent understanding of how lambdas are implemented within JDK8 while also gaining an understanding of streams, internal iteration, short-circuiting and constructor references.. Also check out the JSR's above to get further examples.

I've written a blog on some of the advantages of using lambdas in JDK8 called The Power of the Arrow, also NetBeans 8 has great support for converting constructs to JDK8 which I've also blogged about Migrating to JDK 8 with NetBeans.

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As on 2014  I can finally say that LINQ is finally there in java 8 So no need to find an alternative of LINQ anymore

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JaQu is the LINQ equivalent for Java  Although it was developed for the H2 database  it should work for any database since it uses JDBC

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There is no such feature in java  By using the other API you will get this feature  Like suppose we have a animal Object containing name and id  We have list object having animal objects  Now if we want to get the all the animal name which contains  o  from list object  we can write the following query   from animals  where  getName   contains  o    all     Above Query statement will list of the animals which contains  o  alphabet in their name  More information please go through following blog  http   javaworldwide blogspot in 2012 09 linq-in-java html

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Scala Now i star read it   and found it like linq but more simple and more unreadable  but scala can run at linux yes  csharp need mono

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For basic functional collections  Java 8 has it built in  most of the major non-Java JVM languages have it built in  Scala  Clojure  etc   and you can get add on libs for earlier Java versions   For full language integrated access to a SQL database  Scala  runs on the JVM  has Slick

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

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you can try this library  https   code google com p qood   Here are some reasons to use it    lightweight  only 9 public interface class to learn  query like SQL  support group-by  order-by  left join  formula    etc  for big data  use File QFS  instead of Heap Memory  try to solve Object-relational impedance mismatch

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There is a project called quaere   It s a Java framework which adds the ability to query collections   Note  According to the author  the project is not maintained anymore

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you can use scala  it is similar in syntax and it s actually probably more powerful than linq

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It sounds like the Linq that everyone is talking about here is just LinqToObjects  Which I believe only offers functionality that can already be accomplished today in Java  but with really ugly syntax   What I see as the real power of Linq in  Net is that lambda expressions can be used in a context requiring either a Delegate or an Expression and will then be compiled into the appropriate form  This is what allows things like LinqToSql  or anything other than LinqToObjects  to work  and allows them to have a syntax identical to LinqToObjects   It looks like all of the projects referred to above are only offering the capabilities of LinqToObjects  Which makes me thing that LinqToSql-type functionality is not on the horizon for Java

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You can try out my library CollectionsQuery  It allows to run LINQ like queries over collections of objects   You have to pass predicate  just like in LINQ  If you are using java6 7 than you have to use old syntax with Interfaces   List lt String gt  names   Queryable from people                                       filter new Predicate lt Person gt                                                      public boolean filter Person p                                                        return p age gt 20                                                                                                                                        map    new Converter lt Person String gt                                                      public Integer convert Person p                                                        return p name                                                                                                                                        toList      You can also use it in Java8  or in old java with RetroLambda and it s gradle plugin  then you will have new fancy syntax   List lt String gt  names   Queryable from people                                       filter p- gt p age gt 20                                       map    p- gt p name                                       toList      If you need to run DB queryes  than you can look on JINQ  as mentioned above  but it can t be back-ported by RetroLambda  doe to use of serialized lambdas

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Shameless self plug  you could always use https   github com amoerie jstreams   Works on Java 6 and up  a perfect fit for Android development   It looks a lot like Scala operators  lodash  C  LINQ  etc

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See SBQL4J  It s type-safe strong query language integrated with Java  Allows to write complicated and multiply nested queries  There is a lot of operators  Java methods can be invoked inside queries so as constructors  Queries are translated to pure Java code  there is no reflection at runtime  so execution is very fast   EDIT  Well  so far SBQL4J it s the ONLY extension to Java language which gives query capabilities similar to LINQ  There are some interesting project like Quaere and JaQue but they are only API s  not syntax   semantics extension with strong type safety in compile time

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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

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HQL  Hibernate Query Language  is very similar to Linq in  Net

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Just to add another alternative  Java 6 does have a solution for type-safe database queries using the javax persistence criteria package    Though i must say that this is not really LINQ  because with LINQ you can query any IEnumerable

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There is no equivalent to LINQ for Java   But there is some of the external API which is looks like LINQ such as https   github com nicholas22 jpropel-light  https   code google com p jaque

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You can use Java Functional Utils to convert C  s 101 LINQ examples that s compatible with Java 1 7 on Android

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Not really a  Linq to SQL  equivalent for Java  but something close to it   Query DSL

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Maybe not the answer you re hoping for  but if some part of you code need heavy work on collections  searching  sorting  filtering  transformations  analysis  you may take in consideration to write some classes in Clojure or Scala   Because of their functional nature  working with collections is what they re best at  I don t have much experience with Scala  but with Clojure you d probably find a more powerful Linq at your fingertips and once compiled  the classes you d produce would integrate seamlessy with the rest of the code base

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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

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I tried guava-libraries from google  It has a FluentIterable which I think is close to LINQ  Also see FunctionalExplained   List lt String gt  parts   new ArrayList lt String gt         add parts to the collection      FluentIterable lt Integer gt  partsStartingA        FluentIterable from parts  filter new Predicate lt String gt               Override         public boolean apply final String input                return input startsWith  a                     transform new Function lt String  Integer gt               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

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LINQ to Objects - JAVA 8 has added the Stream API which adds support for functional-style operations on streams of values   Package java util stream  Java 8 Explained  Applying Lambdas to Java Collections  LINQ to SQL NHibernate etc   database querying  - One option would be to use JINQ which also uses the new JAVA 8 features and was released on Feb 26  2014 on Github  https   github com my2iu Jinq     Jinq provides developers an easy and natural way to write database   queries in Java  You can treat database data like normal Java objects   stored in collections  You can iterate over them and filter them using   normal Java commands  and all your code will be automatically   translated into optimized database queries  Finally  LINQ-style   queries are available for Java    JINQ project site  http   www jinq org

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There is nothing like LINQ for Java        Edit  Now with Java 8 we are introduced to the Stream API  this is a similar kind of thing when dealing with collections  but it is not quite the same as Linq   If it is an ORM you are looking for  like Entity Framework  then you can try Hibernate   -

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There s a very good library that you can use for this    Located here  https   github com nicholas22 jpropel-light  Lambdas won t be available until Java 8 though  so using it is a bit different and doesn t feel as natural

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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

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You can select the items in a collection  and much more  in a more readable way by using the lambdaj library  https   code google com archive p lambdaj   It has some advantages over the Quaere library because it doesn t use any magic string  it is completely type safe and in my opinion it offers a more readable DSL

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There was the programming language Pizza  a Java extension  and you should have a look to it  - It uses the concept of  fluent interfaces  to query data in a declarative manner and that is in principle identical to LINQ w o query expressions  http   en wikipedia org wiki Pizza programming language   But alas it was not pursued  but it would have been one way to get something similar to LINQ into Java

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https   code google com p joquery   Supports different possibilities   Given collection   Collection lt Dto gt  testList   new ArrayList lt  gt       of type   class Dto       private int id      private String text       public int getId                 return id             public int getText                 return text            Filter  Java 7  Filter lt Dto gt  query   CQ  lt Dto gt filter testList       where        property  id   eq   value 1   Collection lt Dto gt  filtered   query list      Java 8  Filter lt Dto gt  query   CQ  lt Dto gt filter testList       where        property Dto  getId       eq   value 1   Collection lt Dto gt  filtered   query list      Also   Filter lt Dto gt  query   CQ  lt Dto gt filter            from testList           where            property Dto  getId  between   value 1  value 2           and            property Dto  grtText  in   value new string    a   b       Sorting  also available for the Java 7   Filter lt Dto gt  query   CQ  lt Dto gt filter testList           orderBy            property Dto  getId           property Dto  getName      Collection lt Dto gt  sorted   query list      Grouping  also available for the Java 7   GroupQuery lt Integer Dto gt  query   CQ  lt Dto Dto gt query testList           group            groupBy Dto  getId      Collection lt Grouping lt Integer Dto gt  gt  grouped   query list      Joins  also available for the Java 7   Given   class LeftDto       private int id      private String text       public int getId                 return id             public int getText                 return text           class RightDto       private int id      private int leftId      private String text       public int getId                 return id             public int getLeftId                         return leftId                 public int getText                 return text           class JoinedDto       private int leftId      private int rightId      private String text       public JoinedDto int leftId int rightId String text                this leftId   leftId          this rightId   rightId          this text   text             public int getLeftId                 return leftId             public int getRightId                         return rightId                 public int getText                 return text           Collection lt LeftDto gt  leftList   new ArrayList lt  gt      Collection lt RightDto gt  rightList   new ArrayList lt  gt       Can be Joined like   Collection lt JoinedDto gt  results   CQ  lt LeftDto  LeftDto gt query   from leftList                    lt RightDto  JoinedDto gt innerJoin CQ  lt RightDto  RightDto gt query   from rightList                    on LeftFyo  getId  RightDto  getLeftId                   transformDirect selection - gt   new JoinedDto selection getLeft   getText                                                          selection getLeft   getId                                                          selection getRight   getId                                                        list      Expressions  Filter lt Dto gt  query   CQ  lt Dto gt filter        from testList       where        exec s - gt  s getId     1  eq   value 2

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An anonymous user mentioned another one  Diting      Diting is a class library provides query capabilities on collections through chainable methods and anonymous interface like Linq in  NET  Unlike most of other collection library those are using static methods need iterate whole collection  Diting provides a core Enumerable class whitch contains deffered chainable methods to implement query on collection or array        Supported Methods  any  cast  contact  contains  count  distinct  elementAt  except  first  firstOrDefault  groupBy  interset  join  last  lastOrDefault  ofType  orderBy  orderByDescending  reverse  select  selectMany  single  singleOrDefault  skip  skipWhile  take  takeWhile  toArray  toArrayList  union  where

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You won t find an equivalent of LINQ unless you use the javacc to create your own equivalent   Until that day when someone finds a viable way to do so  there are some good alternatives  such as   jOOQ JINQ JaQue JaQu Linq4j Quaere  No longer maintained  QueryDSL JSR-341

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Check out tiny-q   Note that you currently can t download it    Here s an example adapted the above link      First we need a collection of some data  let s say a set of strings   String   strings      bla    mla    bura    bala    mura    buma          Now we want to select only the strings which start with  b     Query lt String gt  stringsStartingWithB   new Query lt String gt  strings  where      new Query Func lt String  Boolean gt             public Boolean run String in                return in startsWith  b                            No actual data moved copied or anything like that  it will get processed as soon as you start iterating    for String string   stringsStartingWithB         System out println string

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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

[java] What is the Java equivalent for LINQ?

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