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Java Utils - zero dependency library with useful utils

Use this class if you need to do some operations on Java objects, collections, or if you need to generate objects etc.

Installation

Install from Maven Central Repository.

<dependency>
  <groupId>com.github.hadasbro</groupId>
  <artifactId>javautils</artifactId>
  <version>1.0.1</version>
</dependency>

Overview

Library contains some methods to

  1. Handle collections of elements
  2. Print and stringify object of any kind.
  3. Some object utils e.g. POJO < - > DTO converter.
  4. Some additional methods, e.g. Object Coalesce, wrapper for CompletionException, array element exists checker and more

picture

Usage

Code has been splitted for some subclasses as below.

Example objects (see classes below)

Game gameA = null;
User userA = null;
Game gameB = new Game("Game 1", "game1", "category 1");
Game gameC = new Game("Game 2", "game2", "category 2");
Game gameD = new Game("Game 3", "game3", "category 1");
Game gameE = new Game("Game 4", "game4", "category 3");


List<Game> gamesCollection = new LinkedList<>(){{
    add(gameB); add(gameC); add(gameD); add(gameE);
}};

List<Game> gamesCollection2 = new LinkedList<>(){{
    add(gameB);
}};

List<Game> gamesCollection3 = new LinkedList<>(){{
    add(gameC); add(gameD);
}};

List<Game> gamesCollection4 = new LinkedList<>(){{
    add(gameE);
}};

  1. CollectionUtils - methods usefult for handling collections

    a) CollectionUtils::collGroupper - group collection of objects by object's method value / by property

    • signature

      <T extends EntityTag, S> Map<S, Set<T>> collGroupper<T extends EntityTag, S> Map<S, Set<T>> collGroupper(Collection<T> collection,Collector<? super T, ?, Map<S,Set<T>>> collector)

    • usage

      Map<String, Set<Game>> grouppedByCategory = CollectionUtils.collGroupper(
        gamesCollection,
        Game::getCategory
);

    • result

        {category 3=[Game{name='Game 4', gameTag='game4', category='category 3'}],category 2=[Game{name='Game 2', gameTag='game2', category='category 2'}],category 1=[Game{name='Game 1', gameTag='game1', category='category 1'},Game{name='Game 3', gameTag='game3', category='category 1'}]}

    b) CollectionUtils.collGroupperFlatter - group collection of objects by object's method value / by property and flat to object value / property

    • signature

      <T extends EntityTag, S, R> Map<S, Set<R>> collGroupperFlatter(gamesCollection, Game::getCategory, Game::getName);

    • usage

      Map<String, Set<String>> gameNameByCategory = CollectionUtils.collGroupperFlatter(
        gamesCollection,
        Game::getCategory,
        Game::getName
);

    • result

        {category 3=[Game 4], category 2=[Game 2], category 1=[Game 1, Game 3]}

    c) CollectionUtils.advancedTransFilter - collection's filter and transformer

    • signature

      Collection<T> advancedTransFilter(Collection<S> collection, Predicate<S> filter,Function<S,T> transformer)

    • usage

      Collection<Game> gameListNewCategory = CollectionUtils.advancedTransFilter(
        gamesCollection,
        g -> g.getCategory().equals("category 1"),
        g -> {
            g.setCategory("New category");
            return g;
        }
);

    • result

         [Game{name='Game 1', gameTag='game1', category='New category'}, Game{name='Game 3', gameTag='game3', category='New category'}]

    d) CollectionUtils::transformCollection - transform collection using multiple transformers

    • signature

      <T> Collection<T> transformCollection(Collection<T> collection,UnaryOperator<T> ...transformers)

    • usage

      Collection<Game> transformedCollection = CollectionUtils.transformCollection(
        gamesCollection,
        g -> {
            g.setCategory("New category");
            return g;
        },
        g -> {
            g.setName(g.getName().toUpperCase());
            return g;
        },
        g -> {
            g.setGameTag(g.getGameTag().toLowerCase());
            return g;
        }
);

    • result

        [Game{name='GAME 1', gameTag='game1', category='New category'},Game{name='GAME 2', gameTag='game2', category='New category'},Game{name='GAME 3', gameTag='game3', category='New category'},Game{name='GAME 4', gameTag='game4', category='New category'}]

    e) CollectionUtils.findAll - search all elements in collection by predicate

    • signature

      <T> ArrayList<T> findAll(Collection<T> collection, Predicate<T> filter)

    • usage

      ArrayList<Game> gamesFromCategory1 = CollectionUtils.findAll(
        gamesCollection, game -> game.getCategory().equals("New category")
);

    • result

        [Game{name='GAME 1', gameTag='game1', category='New category'},Game{name='GAME 2', gameTag='game2', category='New category'},Game{name='GAME 3', gameTag='game3', category='New category'},Game{name='GAME 4', gameTag='game4', category='New category'}]

    f) CollectionUtils.getRandomElement - get element by index or random if index is out of bound

    • signature

      <T> T getRandomElement(List<T> list, int index)

    • usage

      Game randomGame = CollectionUtils.getRandomElement(gamesCollection, 5);

    • result

        Game{name='GAME 2', gameTag='game2', category='New category'}

    g) CollectionUtils::getFirstFromCollection - get first element from collection

    • signature

      <E> E getFirstFromCollection(Collection<E> collection)

    • usage

      Game firstGame = CollectionUtils.getFirstFromCollection(gamesCollection);

    • result

        Game{name='GAME 1', gameTag='game1', category='New category'}

    h) CollectionUtils::objGenerateSet + CollectionUtils::objGenerate - generate Set/List of objects by supplier

    • signature

      <T> Set<T> objGenerateSet(Integer n, Function<Integer, T> s)
<T> ArrayList<T> objGenerate(Integer n, Function<Integer, T> s)

    • usage

      Set<Game> my5Games = CollectionUtils.objGenerateSet(
        5, i -> new Game("Game " + i, "tag" + i, "category")
);

ArrayList<Game> myAnother5Games = CollectionUtils.objGenerate(
        5, i -> new Game("Game " + i, "tag" + i, "category")
);

    • result

        [Game{name='Game 0', gameTag='tag0', category='category'},Game{name='Game 1', gameTag='tag1', category='category'}, Game{name='Game 2', gameTag='tag2', category='category'},Game{name='Game 3', gameTag='tag3', category='category'}, Game{name='Game 4', gameTag='tag4', category='category'}]
  [Game{name='Game 0', gameTag='tag0', category='category'},Game{name='Game 1', gameTag='tag1', category='category'},Game{name='Game 2', gameTag='tag2', category='category'},Game{name='Game 3', gameTag='tag3', category='category'},Game{name='Game 4', gameTag='tag4', category='category'}]

    i) CollectionUtils::listsCombiner

    • signature

      <T> List<T> listsCombiner(List<? extends T>... lists)

    • usage

      List<Game> combinedList = CollectionUtils.listsCombiner(gamesCollection2, gamesCollection3, gamesCollection4);

    • result

        [Game{name='GAME 1', gameTag='game1', category='New category'},Game{name='GAME 2', gameTag='game2', category='New category'},Game{name='GAME 3', gameTag='game3', category='New category'},Game{name='GAME 4', gameTag='game4', category='New category'}]

    j) CollectionUtils::anyOkFromCollection, CollectionUtils::allNotOkFromCollection, CollectionUtils::allOkFromCollection

    • signatures

      <T> boolean allOkFromCollection(Collection<T> collection, Predicate<? super T> condition)
<T> boolean allNotOkFromCollection(Collection<T> collection, Predicate<? super T> condition)
<T> boolean anyOkFromCollection(Collection<T> collection, Predicate<? super T> condition)

    • usage

      boolean collectionContainsGameCategory1 = CollectionUtils.anyOkFromCollection(
      gamesCollection2,
      game -> game.getCategory().equals("category 1")
);

boolean collectionNotContainsGameCategory1 = CollectionUtils.allNotOkFromCollection(
        gamesCollection2,
        game -> game.getCategory().equals("category 1")
);

boolean collectionContainsOnlyGameCategory1 = CollectionUtils.allOkFromCollection(
        gamesCollection2,
        game -> game.getCategory().equals("category 1")
);

    • result

         false, true, false

  2. ObjectUtils - operations on objects. a) ObjectUtils::convertPojoToDto - convert POJO - > DTO

    • signatures

      <T extends DtoObject, S extends EntityTag> T convertPojoToDto(Class<T> targetClass, S post)
<T extends DtoObject, S extends EntityTag> List<T> convertPojoToDto(Class<T> targetClass, Collection<S> post)

    • usage

          // single object conversion
    GameDto gameDtoResult = ObjectUtils.convertPojoToDto(GameDto.class, gameB);
    
    // collection of POJOs
    List<GameDto> gameDtoResults = ObjectUtils.convertPojoToDto(GameDto.class, new ArrayList<Game>(){{
        add(gameB);
        add(gameC);
        add(gameD);
    }});
    ```

    • result

         GameDto object ( GameDto{name='Game 1'} )
   GameDto objects ( [GameDto{name='Game 1'}, GameDto{name='Game 2'}, GameDto{name='Game 3'}] )

    b) ObjectUtils::convert - convert DTO -> POJO

    • signature

      <T, S> T convert(Class<T> targetClass, S post)

    • usage

      Game game = ObjectUtils.convert(Game.class, gameDtoResult);

    • result

         Game object ( Game{name='Game 1'} )

    see more( https://github.com/glaures/modelprojector )

  3. ThreadUtils - multithread programming utils. a) ThreadUtils::excToCompletableExc - wrap CompletionException exceptions in CompletableFuture

    • signature

      CompletionException excToCompletableExc(Throwable tex)

    • usage

      /*
 * wrap custom exception in completable future and throw
 * to be able to handle this exception later (unwrap and handle)
 */
CompletableFuture.allOf(
        CompletableFuture.supplyAsync(() -> {
            throw ThreadUtils.excToCompletableExc(new CustomException("Example exception"));
        })
)

.handle((res, ex) -> {

    if (ex != null && ex.getCause() instanceof CustomException) {
        return (CustomException) ex.getCause();
    }
    return null;

});

    • result

        you can handle CustomException in .handle() method

  4. General Utils - other useful methods.

    Utils::coalesce

    Utils.coalesce(gameA, userA, gameB, gameC)

Utils.coalesce(
        () -> null,
        () -> gameB,
        () -> gameC
);

// Game{name='Game 1', gameTag='game1', category='category 1'}
// Game{name='Game 1', gameTag='game1', category='category 1'}
// first not null element

    Utils::rand

    int rand1 = Utils.rand(0, 100); // random number from 0 to 100
int rand2 = Utils.rand(115, 200); // random number from 115 to 200

    Utils::getRandString

    String randString = Utils.getRandString(32);
// random string 32 characters (e.g. ppS4NlSGnSTo7HuwPkvIV14HOBUPKdXh)

    Utils::arrayInclude

    String strings[] = {"abc", "def", "ghi"};
Utils.arrayInclude(strings, "def"); // true
Utils.arrayInclude(strings, "defghi"); // false

  5. Object stringifer - var_dump / object printer.

    Interface

    interface Printeable {
    default String stringify() {
        return ToStringBuilder.reflectionToString(this, new ObjectStringifer.PrintToStringStyle());
    }

    default String deepStringify() {
        return (new ObjectStringifer.DeepObjectPrinter()).toString(this);
    }
}

    Usage: Implement this interface if you want your object/class to be stringifeable.

    Example:

    public class Game implements Printeable {} 

Game game = new Game("Game 1", "game1", "category 1");

String gameStr1 = gameB.stringify();
// [name=Game 1,gameTag=game1,category=category 1]

String gameStr2 =  game.deepStringify());
// org.bitbucket.javautils.test.classes.Game[name=Game 1,gameTag=game1,category=category 1][]

// object printers
game.print();
game.deepPrint();

  6. Classes used in examples above

    see source code, package test.classes

Authors

  • Slawomir Hadas - author - Github