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jLinqer

Circle CI Coverage Status Maven Central License: MIT

"jLinqer" is a Java implementation of LINQ.

Maven

<dependency>
    <groupId>com.github.jlinqer</groupId>
    <artifactId>jlinqer</artifactId>
    <version>1.0.1</version>
</dependency>

Usage

The following operations are available.

LINQ - jLinqer Matrix

LINQ(C#) jLinqer (Java 8) Stream (Java 8)
Where where filter
Select select map
OrderBy orderBy sorted
OrderByDescending orderByDescending n/a
ThenBy thenBy n/a
ThenByDescending thenByDescending n/a
SelectMany selectMany flatMap
Skip skip skip
SkipWhile skipWhile n/a
Take take limit
TakeWhile takeWhile n/a
Concat concat concat
Intersect intersect n/a
Union union n/a
Except except n/a
Join join n/a
GroupJoin groupJoin n/a
Reverse reverse n/a
Zip zip n/a
Distinct distinct distinct
Aggregate aggregate reduce
GroupBy groupBy Collectors.groupingBy
Average averageXXX Collectors.summarizingXXX
Count / LongCount count count
Max max max
Min min min
Sum sumXXX Collectors.summarizingXXX
First first findFirst
FirstOrDefault firstOrDefault n/a
Last last n/a
LastOrDefault lastOrDefault n/a
Single single n/a
SingleOrDefault singleOrDefault n/a
DefaultIfEmpty defaultIfEmpty n/a
ElementAt elementAt n/a
ElementAtOrDefault elementAtOrDefault n/a
All all allMatch
Any any anyMatch
Empty empty n/a
Range range n/a
Repeat repeat n/a
SequenceEqual sequenceEqual n/a
Cast cast n/a
OfType ofType n/a

Where

List<Integer> list = new List<>(1, 2, 3);

List<Integer> actual = list.where(x -> x == 1 || x == 3).toList();

assertEquals(true , actual.contains(1));
assertEquals(false, actual.contains(2));
assertEquals(true , actual.contains(3));

Select

List<Person> list = new List<>(
        new Person("React"   , 1),
        new Person("Angular" , 3),
        new Person("Backbone", 5)
);

List<String> actual = list.select(x -> x.name).toList();

assertEquals("React"   , actual.get(0));
assertEquals("Angular" , actual.get(1));
assertEquals("Backbone", actual.get(2));

OrderBy

List<String> list = new List<>("Backbone", "Angular", "React");

List<String> actual = list.orderBy(x -> x).toList();

assertEquals("Angular" , actual.get(0));
assertEquals("Backbone", actual.get(1));
assertEquals("React"   , actual.get(2));

OrderByDescending

List<String> list = new List<>("Backbone", "Angular", "React");

List<String> actual = list.orderByDescending(x -> x).toList();

assertEquals("React"   , actual.get(0));
assertEquals("Backbone", actual.get(1));
assertEquals("Angular" , actual.get(2));

ThenBy

List<Person> list = new List<>(
        new Person("Angular2", 2),
        new Person("Angular1", 2),
        new Person("React"   , 1)
);

List<String> actual = list.orderBy(x -> x.age).thenBy(x -> x.name).toList();

assertEquals("React" , actual.get(0).name);
assertEquals("Angular1", actual.get(1).name);
assertEquals("Angular2"   , actual.get(2).name);

ThenByDescending

List<Person> list = new List<>(
        new Person("Angular2", 2),
        new Person("Angular1", 2),
        new Person("React"   , 1)
);

List<String> actual = list.orderBy(x -> x.age).thenByDescending(x -> x.name).toList();

assertEquals("React" , actual.get(0).name);
assertEquals("Angular2", actual.get(1).name);
assertEquals("Angular1"   , actual.get(2).name);

SelectMany

List<Person> list = new List<>(
        new Person("Angular", 3, new List("1.0.1", "1.0.2")),
        new Person("React"  , 1, new List("2.0.1", "2.0.2"))
);

List<String> actual = list.selectMany(x -> x.versionHistory).toList();

assertEquals("1.0.1", actual.get(0));
assertEquals("1.0.2", actual.get(1));
assertEquals("2.0.1", actual.get(2));
assertEquals("2.0.2", actual.get(3));

Skip

List<Integer> list = new List<>(1, 2, 3);

List<Integer> actual = list.skip(2).toList();

assertEquals(3, actual.get(0).intValue());

SkipWhile

List<Integer> list = new List<>(1, 2, 3, 4, 5);

List<Integer> actual = list.skipWhile(x -> x <= 3).toList();

assertEquals(4, actual.get(0).intValue());
assertEquals(5, actual.get(1).intValue());

Take

List<String> list = new List<>("Backbone", "Angular", "React");

List<String> actual = list.take(2).toList();

assertEquals(2, actual.size());
assertEquals("Backbone", actual.get(0));
assertEquals("Angular" , actual.get(1));

TakeWhile

List<String> list = new List<>("Backbone", "Angular", "React");

List<String> actual = list.takeWhile(x -> x.equals("Backbone") || x.equals("Angular")).toList();

assertEquals(2, actual.size());
assertEquals("Backbone", actual.get(0));
assertEquals("Angular" , actual.get(1));

Concat

List<Integer> first  = new List<>(1, 2);
List<Integer> second = new List<>(2, 3);

List<Integer> actual = first.concat(second).toList();

assertEquals(1, actual.get(0).intValue());
assertEquals(2, actual.get(1).intValue());
assertEquals(2, actual.get(2).intValue());
assertEquals(3, actual.get(3).intValue());

Intersect

List<Integer> first  = new List<>(1, 2, 3);
List<Integer> second = new List<>(1, 3);

List<Integer> actual = first.intersect(second).toList();

assertEquals(1, actual.get(0).intValue());
assertEquals(3, actual.get(1).intValue());

Union

List<Integer> first = new List<>(1, 2, 3);
List<Integer> second = new List<>(0, 1, 3, 4);

List<Integer> actual = first.union(second).toList();

assertEquals(5, actual.size());
assertEquals(1, actual.get(0).intValue());
assertEquals(2, actual.get(1).intValue());
assertEquals(3, actual.get(2).intValue());
assertEquals(0, actual.get(3).intValue());
assertEquals(4, actual.get(4).intValue());

Except

List<Integer> first  = new List<>(1, 2, 3);
List<Integer> second = new List<>(1, 3);

List<Integer> actual = first.except(second).toList();

assertEquals(2, actual.get(0).intValue());

Join

List<Javascript> outer = new List<>(
        new Javascript("Angular", 1),
        new Javascript("React"  , 4),
        new Javascript("ES2016" , 5)
);
List<Javascript> inner = new List<>(
        new Javascript("Angular", 2),
        new Javascript("Angular", 3),
        new Javascript("ES2016" , 6),
        new Javascript("ES7"    , 7)
);

Function<Javascript, String> outerKey = (x) -> x.name;
Function<Javascript, String> innerKey = (y) -> y.name;
BiFunction<Javascript, Javascript, Javascript> selector = (x, y) -> new Javascript(x.name, y.age);
List<Javascript> actual = outer.join(inner, outerKey, innerKey, selector).toList();

assertEquals(3, actual.size());
assertEquals("Angular", actual.get(0).name);
assertEquals("Angular", actual.get(1).name);
assertEquals("ES2016" , actual.get(2).name);
assertEquals(2, actual.get(0).age);
assertEquals(3, actual.get(1).age);
assertEquals(6, actual.get(2).age);

GroupJoin

List<Javascript> outer = new List<>(
        new Javascript("Angular", 1),
        new Javascript("React"  , 4),
        new Javascript("ES2016" , 5)
);
List<Javascript> inner = new List<>(
        new Javascript("Angular", 2),
        new Javascript("Angular", 3),
        new Javascript("ES2016" , 6),
        new Javascript("ES7"    , 7)
);

Function<Javascript, String> outerKey = (x) -> x.name;
Function<Javascript, String> innerKey = (y) -> y.name;
BiFunction<Javascript, IEnumerable<Javascript>, Javascript> selector = (x, y) -> new Javascript(x.name, y.select(z -> z.age));
List<Javascript> actual = outer.groupJoin(inner, outerKey, innerKey, selector).toList();

assertEquals(3, actual.size());
assertEquals("Angular", actual.get(0).name);
assertEquals("React"  , actual.get(1).name);
assertEquals("ES2016" , actual.get(2).name);
assertEquals(2, actual.get(0).ages.elementAt(0));
assertEquals(3, actual.get(0).ages.elementAt(1));
assertEquals(0, actual.get(1).ages.count());
assertEquals(6, actual.get(2).ages.elementAt(0));

Reverse

List<Integer> list = new List<>(1, 2, 3);

List<Integer> actual = list.reverse().toList();

assertEquals(3, actual.get(0).intValue());
assertEquals(2, actual.get(1).intValue());
assertEquals(1, actual.get(2).intValue());

Zip

List<Integer> first = new List<>(1, 2, 3);
List<String> second = new List<>("Angular", "React", "Backbone");

List<Integer> actual = first.zip(second, (x, y) -> String.format("%s %d", x, y)).toList();

assertEquals("1 Angular" , actual.get(0));
assertEquals("2 React"   , actual.get(1));
assertEquals("3 Backbone", actual.get(2));

Distinct

List<Integer> list =
        new List<>(
                1, 2, 3,
                1, 2, 3, 4
        );

List<Integer> actual = list.distinct().toList();

assertEquals(1, actual.get(0).intValue());
assertEquals(2, actual.get(1).intValue());
assertEquals(3, actual.get(2).intValue());
assertEquals(4, actual.get(3).intValue());

Aggregate

List<Integer> list = new List<>(1, 2, 3);

int actual = list.aggregate((sum, elem) -> sum + elem);

assertEquals(6, actual);

GroupBy

List<Person> list = new List<>(
        new Person("React"   , 1),
        new Person("Angular" , 1),
        new Person("Backbone", 5)
);

Map<Integer, IEnumerable<Person>> actual = list.groupBy(x -> x.age);

assertEquals(true, actual.get(1).any(x -> x.name.equals("React")));
assertEquals(true, actual.get(1).any(x -> x.name.equals("Angular")));
assertEquals(true, actual.get(5).any(x -> x.name.equals("Backbone")));

Average

List<Long> listLong = new List<>(1l, 2l, 3l, 4l);

double actualLong = listLong.averageLong(x -> x);

assertEquals(2.5d, actualLong, 0);

Count

List<String> list = new List<>("Backbone", "Angular", "React");

long actual = list.longCount();
int actualNone = list.count(x -> x.equals("jquery"));

assertEquals(3, actual);
assertEquals(0, actualNone);

Max

List<Double> listDouble = new List<>(1d, 2d, 3d);

double actualDouble = listDouble.max(x -> x);

assertEquals(3d, actualDouble, 0);

Min

List<BigDecimal> listBigDecimal = new List<>(
        new BigDecimal(1d),
        new BigDecimal(2d),
        new BigDecimal(3d)
);

BigDecimal actualBigDecimal = listBigDecimal.min(x -> x);

assertEquals(1d, actualBigDecimal.doubleValue(), 0);

Sum

List<Integer> listInt = new List<>(1, 2, 3);

int actualInt = listInt.sumInt(x -> x);

assertEquals(6, actualInt);

FirstOrDefault

List<String> list = new List<>("Backbone", "Angular", "React");

String actualFirst   = list.firstOrDefault();
String actualMatch   = list.firstOrDefault(x -> x.equals("Angular"));
String actualUnMatch = list.firstOrDefault(x -> x.equals("jquery"));

assertEquals("Backbone", actualFirst);
assertEquals("Angular" , actualMatch);
assertEquals(null      , actualUnMatch);

LastOrDefault

List<Integer> list = new List<>(1, 2, 3);
List<Integer> listEmpty = new List<>();

int actual = list.lastOrDefault();
Integer actualDefaultNone = listEmpty.lastOrDefault(x -> x == 0);

assertEquals(3, actual);
assertEquals(null, actualDefaultNone);

SingleOrDefault

List<Integer> listMany = new List<>(1, 2, 3);
List<Integer> listEmpty = new List<>();

int actualFilter = listMany.singleOrDefault(x -> x == 3);
Integer actualUnMatch = listEmpty.singleOrDefault(x -> x == 0);

assertEquals(3, actualFilter);
assertEquals(null, actualUnMatch);

DefaultIfEmpty

List<String> listEmpty = new List<>();

List<String> actualDefault = listEmpty.defaultIfEmpty("ES7").toList();

assertEquals("ES7", actualDefault.get(0));

ElementAtOrDefault

List<Integer> list = new List<>(1, 2, 3);

int actual = list.elementAtOrDefault(2);
Integer actualDefault = list.elementAtOrDefault(3);

assertEquals(3, actual);
assertEquals(null, actualDefault);

All

List<String> list = new List<>("Backbone", "Angular", "React");

boolean actual = list.all(x -> x.equals("Angular") || x.equals("Backbone") || x.equals("React"));
boolean actualNotFound = list.all(x -> x.equals("Angular") || x.equals("React"));

assertEquals(true, actual);
assertEquals(false, actualNotFound);

Any

List<String> list = new List<>("Backbone", "Angular", "React");

boolean actual = list.any(x -> x.equals("Angular"));
boolean actualNotFound = list.any(x -> x.equals("jquery"));

assertEquals(true, actual);
assertEquals(false, actualNotFound);

Empty

List<Double> actual = IEnumerable.empty(Double.class);

assertEquals(0, actual.count());

Range

List<Integer> actual = IEnumerable.range(-2, 3);

assertEquals(-2, actual.get(0).intValue());
assertEquals(-1, actual.get(1).intValue());
assertEquals(0 , actual.get(2).intValue());

Repeat

List<String> actual = IEnumerable.repeat(String.class, "Law of Cycles", 10);

assertEquals(10, actual.count());
assertEquals("Law of Cycles", actual.get(9));

SequenceEqual

List<Integer> first = new List<>(1, 2, 3);
List<Integer> secondMatch = new List<>(1, 2, 3);
List<Integer> secondUnMatchElem = new List<>(1, 2, 4);

boolean actualMatch = first.sequenceEqual(secondMatch);
boolean actualUnMatchElm = first.sequenceEqual(secondUnMatchElem);

assertEquals(true, actualMatch);
assertEquals(false, actualUnMatchElm);

Cast

List<Object> list = new List<>(1, 2, 3);

List<Integer> actual = list.cast(Integer.class).toList();

assertEquals(1, actual.get(0).intValue());
assertEquals(2, actual.get(1).intValue());
assertEquals(3, actual.get(2).intValue());

OfType

List<Object> list = new List<>(1, "2", 3, "4");

List<String>  actualStr = list.ofType(String.class).toList();
List<Integer> actualInt = list.ofType(Integer.class).toList();

assertEquals("2", actualStr.get(0));
assertEquals("4", actualStr.get(1));
assertEquals(1  , actualInt.get(0).intValue());
assertEquals(3  , actualInt.get(1).intValue());

References

  1. Microsoft Reference Source, "Enumerable.cs", http://referencesource.microsoft.com/#System.Core/System/Linq/Enumerable.cs
  2. GitHub, "javaLinq", https://github.com/sircodesalotOfTheRound/javaLinq
  3. Qiita, "LINQ to Objects と Java8-Stream API の対応表", http://qiita.com/amay077/items/9d2941283c4a5f61f302
  4. stackoverflow, "Generic method to perform a map-reduce operation. (Java-8)", http://stackoverflow.com/questions/30826674/generic-method-to-perform-a-map-reduce-operation-java-8

About

"jLinqer" is a Java implementation of LINQ.

qiita.com/kasecato/items/ec7ab8b392fa8bb0a732

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v1.0.1 Latest
May 19, 2018
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