Package org.eclipse.collections.api

Interface LazyIterable<T>

All Superinterfaces:
InternalIterable<T>, Iterable<T>, RichIterable<T>
All Known Implementing Classes:
AbstractLazyIterable, ChunkBooleanIterable, ChunkByteIterable, ChunkCharIterable, ChunkDoubleIterable, ChunkFloatIterable, ChunkIntIterable, ChunkIterable, ChunkLongIterable, ChunkShortIterable, CollectBooleanToObjectIterable, CollectByteToObjectIterable, CollectCharToObjectIterable, CollectDoubleToObjectIterable, CollectFloatToObjectIterable, CollectIntToObjectIterable, CollectIterable, CollectLongToObjectIterable, CollectShortToObjectIterable, CompositeIterable, DistinctIterable, DropIterable, DropWhileIterable, FlatCollectBooleanToObjectIterable, FlatCollectByteToObjectIterable, FlatCollectCharToObjectIterable, FlatCollectDoubleToObjectIterable, FlatCollectFloatToObjectIterable, FlatCollectIntToObjectIterable, FlatCollectIterable, FlatCollectLongToObjectIterable, FlatCollectShortToObjectIterable, Interval, LazyIterableAdapter, RejectIterable, ReverseIterable, SelectInstancesOfIterable, SelectIterable, TakeIterable, TakeWhileIterable, TapIterable, ZipIterable, ZipWithIndexIterable
public interface LazyIterable<T>
extends RichIterable<T>
A LazyIterable is RichIterable which will defer evaluation for certain methods like select, reject, collect, etc. Any methods that do not return a LazyIterable when called will cause evaluation to be forced.
Since:
1.0

  • Method Details

    • getFirst

      T getFirst()
      Description copied from interface: RichIterable
      Returns the first element of an iterable. In the case of a List it is the element at the first index. In the case of any other Collection, it is the first element that would be returned during an iteration. If the iterable is empty, null is returned. If null is a valid element of the container, then a developer would need to check to see if the iterable is empty to validate that a null result was not due to the container being empty.

      The order of Sets are not guaranteed (except for TreeSets and other Ordered Set implementations), so if you use this method, the first element could be any element from the Set.

      Specified by:
      getFirst in interface RichIterable<T>

    • select

      LazyIterable<T> select​(Predicate<? super T> predicate)
      Creates a deferred iterable for selecting elements from the current iterable.
      Specified by:
      select in interface RichIterable<T>

    • selectWith

      <P> LazyIterable<T> selectWith​(Predicate2<? super T,​? super P> predicate, P parameter)
      Description copied from interface: RichIterable
      Similar to RichIterable.select(Predicate), except with an evaluation parameter for the second generic argument in Predicate2.

      E.g. return a Collection of Person elements where the person has an age greater than or equal to 18 years

      Example using a Java 8 lambda expression: 

       RichIterable<Person> selected =
     people.selectWith((Person person, Integer age) -> person.getAge()>= age, Integer.valueOf(18));

      Example using an anonymous inner class: 

       RichIterable<Person> selected =
     people.selectWith(new Predicate2<Person, Integer>()
     {
         public boolean accept(Person person, Integer age)
         {
             return person.getAge()>= age;
         }
     }, Integer.valueOf(18));
      Specified by:
      selectWith in interface RichIterable<T>
      Parameters:
      predicate - a Predicate2 to use as the select criteria
      parameter - a parameter to pass in for evaluation of the second argument P in predicate
      See Also:
      RichIterable.select(Predicate)

    • selectInstancesOf

      <S> LazyIterable<S> selectInstancesOf​(Class<S> clazz)
      Description copied from interface: RichIterable
      Returns all elements of the source collection that are instances of the Class clazz. 
       RichIterable<Integer> integers =
     List.mutable.with(new Integer(0), new Long(0L), new Double(0.0)).selectInstancesOf(Integer.class);
      Specified by:
      selectInstancesOf in interface RichIterable<T>

    • reject

      LazyIterable<T> reject​(Predicate<? super T> predicate)
      Creates a deferred iterable for rejecting elements from the current iterable.
      Specified by:
      reject in interface RichIterable<T>
      Parameters:
      predicate - a Predicate to use as the reject criteria
      Returns:
      a RichIterable that contains elements that cause Predicate.accept(Object) method to evaluate to false

    • rejectWith

      <P> LazyIterable<T> rejectWith​(Predicate2<? super T,​? super P> predicate, P parameter)
      Description copied from interface: RichIterable
      Similar to RichIterable.reject(Predicate), except with an evaluation parameter for the second generic argument in Predicate2.

      E.g. return a Collection of Person elements where the person has an age greater than or equal to 18 years

      Example using a Java 8 lambda expression: 

       RichIterable<Person> rejected =
     people.rejectWith((Person person, Integer age) -> person.getAge() < age, Integer.valueOf(18));

      Example using an anonymous inner class: 

       MutableList<Person> rejected =
     people.rejectWith(new Predicate2<Person, Integer>()
     {
         public boolean accept(Person person, Integer age)
         {
             return person.getAge() < age;
         }
     }, Integer.valueOf(18));
      Specified by:
      rejectWith in interface RichIterable<T>
      Parameters:
      predicate - a Predicate2 to use as the select criteria
      parameter - a parameter to pass in for evaluation of the second argument P in predicate
      See Also:
      RichIterable.select(Predicate)

    • collect

      <V> LazyIterable<V> collect​(Function<? super T,​? extends V> function)
      Creates a deferred iterable for collecting elements from the current iterable.
      Specified by:
      collect in interface RichIterable<T>

    • collectWith

      <P,​ V> LazyIterable<V> collectWith​(Function2<? super T,​? super P,​? extends V> function, P parameter)
      Description copied from interface: RichIterable
      Same as RichIterable.collect(Function) with a Function2 and specified parameter which is passed to the block.

      Example using a Java 8 lambda expression: 

       RichIterable<Integer> integers =
     Lists.mutable.with(1, 2, 3).collectWith((each, parameter) -> each + parameter, Integer.valueOf(1));

      Example using an anonymous inner class: 

       Function2<Integer, Integer, Integer> addParameterFunction =
     new Function2<Integer, Integer, Integer>()
     {
         public Integer value(Integer each, Integer parameter)
         {
             return each + parameter;
         }
     };
 RichIterable<Integer> integers =
     Lists.mutable.with(1, 2, 3).collectWith(addParameterFunction, Integer.valueOf(1));
      Specified by:
      collectWith in interface RichIterable<T>
      Parameters:
      function - A Function2 to use as the collect transformation function
      parameter - A parameter to pass in for evaluation of the second argument P in function
      Returns:
      A new RichIterable that contains the transformed elements returned by Function2.value(Object, Object)
      See Also:
      RichIterable.collect(Function)

    • collectIf

      <V> LazyIterable<V> collectIf​(Predicate<? super T> predicate, Function<? super T,​? extends V> function)
      Creates a deferred iterable for selecting and collecting elements from the current iterable.
      Specified by:
      collectIf in interface RichIterable<T>

    • take

      LazyIterable<T> take​(int count)
      Creates a deferred take iterable for the current iterable using the specified count as the limit.

    • drop

      LazyIterable<T> drop​(int count)
      Creates a deferred drop iterable for the current iterable using the specified count as the limit.

    • takeWhile

      LazyIterable<T> takeWhile​(Predicate<? super T> predicate)
      Since:
      8.0
      See Also:
      OrderedIterable.takeWhile(Predicate)

    • dropWhile

      LazyIterable<T> dropWhile​(Predicate<? super T> predicate)
      Since:
      8.0
      See Also:
      OrderedIterable.dropWhile(Predicate)

    • distinct

      LazyIterable<T> distinct()
      Creates a deferred distinct iterable to get distinct elements from the current iterable.
      Since:
      5.0

    • flatCollect

      <V> LazyIterable<V> flatCollect​(Function<? super T,​? extends Iterable<V>> function)
      Creates a deferred flattening iterable for the current iterable.
      Specified by:
      flatCollect in interface RichIterable<T>
      Parameters:
      function - The Function to apply
      Returns:
      a new flattened collection produced by applying the given function

    • flatCollectWith

      default <P,​ V> LazyIterable<V> flatCollectWith​(Function2<? super T,​? super P,​? extends Iterable<V>> function, P parameter)
      Specified by:
      flatCollectWith in interface RichIterable<T>
      Since:
      9.2

    • concatenate

      LazyIterable<T> concatenate​(Iterable<T> iterable)
      Creates a deferred iterable that will join this iterable with the specified iterable.

    • zip

      <S> LazyIterable<Pair<T,​S>> zip​(Iterable<S> that)
      Creates a deferred zip iterable.
      Specified by:
      zip in interface RichIterable<T>
      Type Parameters:
      S - the type of the second half of the returned pairs
      Parameters:
      that - The RichIterable providing the second half of each result pair
      Returns:
      A new RichIterable containing pairs consisting of corresponding elements of this RichIterable and that. The length of the returned RichIterable is the minimum of the lengths of this RichIterable and that.

    • zipWithIndex

      LazyIterable<Pair<T,​Integer>> zipWithIndex()
      Creates a deferred zipWithIndex iterable.
      Specified by:
      zipWithIndex in interface RichIterable<T>
      Returns:
      A new RichIterable containing pairs consisting of all elements of this RichIterable paired with their index. Indices start at 0.
      See Also:
      RichIterable.zip(Iterable)

    • chunk

      LazyIterable<RichIterable<T>> chunk​(int size)
      Creates a deferred chunk iterable.
      Specified by:
      chunk in interface RichIterable<T>
      Parameters:
      size - the number of elements per chunk
      Returns:
      A RichIterable containing RichIterables of size size, except the last will be truncated if the elements don't divide evenly.

    • tap

      LazyIterable<T> tap​(Procedure<? super T> procedure)
      Creates a deferred tap iterable.
      Specified by:
      tap in interface RichIterable<T>
      See Also:
      RichIterable.each(Procedure), RichIterable.forEach(Procedure)

    • into

      <R extends Collection<T>> R into​(R target)
      Iterates over this iterable adding all elements into the target collection.
      Specified by:
      into in interface RichIterable<T>

    • collectBoolean

      LazyBooleanIterable collectBoolean​(BooleanFunction<? super T> booleanFunction)
      Returns a lazy BooleanIterable which will transform the underlying iterable data to boolean values based on the booleanFunction.
      Specified by:
      collectBoolean in interface RichIterable<T>

    • collectByte

      LazyByteIterable collectByte​(ByteFunction<? super T> byteFunction)
      Returns a lazy ByteIterable which will transform the underlying iterable data to byte values based on the byteFunction.
      Specified by:
      collectByte in interface RichIterable<T>

    • collectChar

      LazyCharIterable collectChar​(CharFunction<? super T> charFunction)
      Returns a lazy CharIterable which will transform the underlying iterable data to char values based on the charFunction.
      Specified by:
      collectChar in interface RichIterable<T>

    • collectDouble

      LazyDoubleIterable collectDouble​(DoubleFunction<? super T> doubleFunction)
      Returns a lazy DoubleIterable which will transform the underlying iterable data to double values based on the doubleFunction.
      Specified by:
      collectDouble in interface RichIterable<T>

    • collectFloat

      LazyFloatIterable collectFloat​(FloatFunction<? super T> floatFunction)
      Returns a lazy FloatIterable which will transform the underlying iterable data to float values based on the floatFunction.
      Specified by:
      collectFloat in interface RichIterable<T>

    • collectInt

      LazyIntIterable collectInt​(IntFunction<? super T> intFunction)
      Returns a lazy IntIterable which will transform the underlying iterable data to int values based on the intFunction.
      Specified by:
      collectInt in interface RichIterable<T>

    • collectLong

      LazyLongIterable collectLong​(LongFunction<? super T> longFunction)
      Returns a lazy LongIterable which will transform the underlying iterable data to long values based on the longFunction.
      Specified by:
      collectLong in interface RichIterable<T>

    • collectShort

      LazyShortIterable collectShort​(ShortFunction<? super T> shortFunction)
      Returns a lazy ShortIterable which will transform the underlying iterable data to short values based on the shortFunction.
      Specified by:
      collectShort in interface RichIterable<T>