Module org.eclipse.xtext.xbase.lib
Package org.eclipse.xtext.xbase.lib

Class IterableExtensions

java.lang.Object
org.eclipse.xtext.xbase.lib.IterableExtensions
@GwtCompatible public class IterableExtensions extends Object
This is an extension library for iterables.
Author:
Sven Efftinge - Initial contribution and API, Sebastian Zarnekow

  • Constructor Summary

    Constructors
    Constructor
    Description
    IterableExtensions()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static boolean
    contains(Iterable<?> iterable, Object o)
    Returns true if this Iterable contains the specified element.
    static <T> Iterable<T>
    drop(Iterable<T> iterable, int count)
    Returns a view on this iterable that provides all elements except the first count entries.
    static <T> Iterable<T>
    dropWhile(Iterable<? extends T> iterable, Functions.Function1<? super T,Boolean> predicate)
    Returns an Iterable containing all elements starting from the first element for which the drop-predicate returned false.
    static boolean
    elementsEqual(Iterable<?> iterable, Iterable<?> other)
    Determines whether two iterables contain equal elements in the same order.
    static <T> boolean
    exists(Iterable<T> iterable, Functions.Function1<? super T,Boolean> predicate)
    Returns true if one or more elements in iterable satisfy the predicate.
    static <T> Iterable<T>
    filter(Iterable<?> unfiltered, Class<T> type)
    Returns all instances of class type in unfiltered.
    static <T> Iterable<T>
    filter(Iterable<T> unfiltered, Functions.Function1<? super T,Boolean> predicate)
    Returns the elements of unfiltered that satisfy a predicate.
    static <T> Iterable<T>
    filterNull(Iterable<T> unfiltered)
    Returns a new iterable filtering any null references.
    static <T> T
    findFirst(Iterable<T> iterable, Functions.Function1<? super T,Boolean> predicate)
    Finds the first element in the given iterable that fulfills the predicate.
    static <T> T
    findLast(Iterable<T> iterable, Functions.Function1<? super T,Boolean> predicate)
    Finds the last element in the given iterable that fulfills the predicate.
    static <T, R> Iterable<R>
    flatMap(Iterable<T> original, Functions.Function1<? super T,? extends Iterable<R>> transformation)
    Returns an iterable that performs the given transformation for each element of original when requested.
    static <T> Iterable<T>
    flatten(Iterable<? extends Iterable<? extends T>> inputs)
    Combines multiple iterables into a single iterable.
    static <T, R> R
    fold(Iterable<T> iterable, R seed, Functions.Function2<? super R,? super T,? extends R> function)
    Applies the combinator function to all elements of the iterable in turn and uses seed as the start value.
    static <T> boolean
    forall(Iterable<T> iterable, Functions.Function1<? super T,Boolean> predicate)
    Returns true if every element in iterable satisfies the predicate.
    static <T> void
    forEach(Iterable<T> iterable, Procedures.Procedure1<? super T> procedure)
    Applies procedure for each element of the given iterable.
    static <T> void
    forEach(Iterable<T> iterable, Procedures.Procedure2<? super T,? super Integer> procedure)
    Applies procedure for each element of the given iterable.
    static <K, V> Map<K,List<V>>
    groupBy(Iterable<? extends V> values, Functions.Function1<? super V,? extends K> computeKeys)
    Returns a map for which the Map.values() is a collection of lists, where the elements in the list will appear in the order as they appeared in the iterable.
    static <T> T
    head(Iterable<T> iterable)
    Returns the first element in the given iterable or null if empty.
    static <A> Iterable<Pair<Integer,A>>
    indexed(Iterable<? extends A> iterable)
    Returns an Iterable of Pairs where the nth pair is created by taking the nth element of the source as the value its 0-based index as the key.
    static boolean
    isEmpty(Iterable<?> iterable)
    Determines if the given iterable contains no elements.
    static boolean
    isNullOrEmpty(Iterable<?> iterable)
    Determines if the given iterable is null or contains no elements.
    static String
    join(Iterable<?> iterable)
    Returns the concatenated string representation of the elements in the given iterable.
    static String
    join(Iterable<?> iterable, CharSequence separator)
    Returns the concatenated string representation of the elements in the given iterable.
    static <T> String
    join(Iterable<T> iterable, CharSequence before, CharSequence separator, CharSequence after, Functions.Function1<? super T,? extends CharSequence> function)
    Returns the concatenated string representation of the elements in the given iterable.
    static <T> String
    join(Iterable<T> iterable, CharSequence separator, Functions.Function1<? super T,? extends CharSequence> function)
    Returns the concatenated string representation of the elements in the given iterable.
    static <T> T
    last(Iterable<T> iterable)
    Deprecated.
    Use #lastOrNull(Iterable<T>) instead: in Java 21, the method getLast has been introduced to some collection classes and would be preferred to this one by the Xbase/Xtend compiler, breaking the semantics of the original code: The Java 21 getLast method throws a NoSuchElementException when the collection is empty, instead of returning null.
    static <T> T
    lastOrNull(Iterable<T> iterable)
    Returns the last element in the given iterable or null if empty.
    static <T, R> Iterable<R>
    map(Iterable<T> original, Functions.Function1<? super T,? extends R> transformation)
    Returns an iterable that performs the given transformation for each element of original when requested.
    static <T extends Comparable<? super T>>
    T
    max(Iterable<T> iterable)
    Finds the maximum of the elements according to their natural ordering.
    static <T> T
    max(Iterable<T> iterable, Comparator<? super T> comparator)
    Finds the maximum element according to comparator.
    static <T, C extends Comparable<? super C>>
    T
    maxBy(Iterable<T> iterable, Functions.Function1<? super T,C> compareBy)
    Finds the element that yields the maximum value when passed to compareBy If there are several maxima, the first one will be returned.
    static <T extends Comparable<? super T>>
    T
    min(Iterable<T> iterable)
    Finds the minimum of the given elements according to their natural ordering.
    static <T> T
    min(Iterable<T> iterable, Comparator<? super T> comparator)
    Finds the mininmum element according to comparator.
    static <T, C extends Comparable<? super C>>
    T
    minBy(Iterable<T> iterable, Functions.Function1<? super T,C> compareBy)
    Finds the element that yields the minimum value when passed to compareBy.
    static <T> Iterable<T>
    operator_plus(Iterable<? extends T> a, Iterable<? extends T> b)
    Concatenates two iterables into a single iterable.
    static <T> T
    reduce(Iterable<? extends T> iterable, Functions.Function2<? super T,? super T,? extends T> function)
    Applies the combinator function to all elements of the iterable in turn.
    static <T> Iterable<T>
    reject(Iterable<T> unfiltered, Class<?> type)
    Returns the elements of unfiltered that are not instanceof type.
    static <T> Iterable<T>
    reject(Iterable<T> unfiltered, Functions.Function1<? super T,Boolean> predicate)
    Returns the elements of unfiltered that do not satisfy a predicate.
    static int
    size(Iterable<?> iterable)
    Returns the number of elements in iterable.
    static <T extends Comparable<? super T>>
    List<T>
    sort(Iterable<T> iterable)
    Creates a sorted list that contains the items of the given iterable.
    static <T> List<T>
    sort(Iterable<T> iterable, Comparator<? super T> comparator)
    Deprecated.
    Use sortWith(Iterable, Comparator) instead.
    static <T, C extends Comparable<? super C>>
    List<T>
    sortBy(Iterable<T> iterable, Functions.Function1<? super T,C> key)
    Creates a sorted list that contains the items of the given iterable.
    static <T> List<T>
    sortWith(Iterable<T> iterable, Comparator<? super T> comparator)
    Creates a sorted list that contains the items of the given iterable.
    static <T> Iterable<T>
    tail(Iterable<T> iterable)
    Returns a view on this iterable that contains all the elements except the first.
    static <T> Iterable<T>
    take(Iterable<T> iterable, int count)
    Returns a view on this iterable that provides at most the first count entries.
    static <T> Iterable<T>
    takeWhile(Iterable<? extends T> iterable, Functions.Function1<? super T,Boolean> predicate)
    Returns an Iterable containing all elements starting from the head of the source up to and excluding the first element that violates the predicate The resulting Iterable is a lazily computed view, so any modifications to the underlying Iterables will be reflected on subsequent iterations.
    static <K, V> Map<K,V>
    toInvertedMap(Iterable<? extends K> keys, Functions.Function1<? super K,V> computeValues)
    Returns a map for which the Map.values() are computed by the given function, and each key is an element in the given keys.
    static <T> List<T>
    toList(Iterable<T> iterable)
    Returns a list that contains all the entries of the given iterable in the same order.
    static <T, K, V> Map<K,V>
    toMap(Iterable<? extends T> inputs, Functions.Function1<? super T,K> computeKeys, Functions.Function1<? super T,V> computeValues)
    Returns a map for which the Map.values() are the product of invoking supplied function computeValues on input iterable elements, and each key is the product of invoking a supplied function computeKeys on same elements.
    static <K, V> Map<K,V>
    toMap(Iterable<? extends V> values, Functions.Function1<? super V,K> computeKeys)
    Returns a map for which the Map.values() are the given elements in the given order, and each key is the product of invoking a supplied function computeKeys on its corresponding value.
    static <T> Set<T>
    toSet(Iterable<T> iterable)
    Returns a set that contains all the unique entries of the given iterable in the order of their appearance.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • IterableExtensions

      public IterableExtensions()

  • Method Details

    • operator_plus

      @Pure public static <T> Iterable<T> operator_plus(Iterable<? extends T> a, Iterable<? extends T> b)

      Concatenates two iterables into a single iterable. The returned iterable has an iterator that traverses the elements in a, followed by the elements in b. The resulting iterable is effectivly a view on the source iterables. That is, the source iterators are not polled until necessary and the result will reflect changes in the sources.

      The returned iterable's iterator supports remove() when the corresponding input iterator supports it.

      Parameters:
      a - the first iterable. May not be null.
      b - the second iterable. May not be null.
      Returns:
      a combined iterable. Never null.

    • findFirst

      public static <T> T findFirst(Iterable<T> iterable, Functions.Function1<? super T,Boolean> predicate)
      Finds the first element in the given iterable that fulfills the predicate. If none is found or the iterable is empty, null is returned.
      Parameters:
      iterable - the iterable. May not be null.
      predicate - the predicate. May not be null.
      Returns:
      the first element in the iterable for which the given predicate returns true, returns null if no element matches the predicate or the iterable is empty.

    • findLast

      public static <T> T findLast(Iterable<T> iterable, Functions.Function1<? super T,Boolean> predicate)
      Finds the last element in the given iterable that fulfills the predicate. If none is found or the iterable is empty, null is returned.
      Parameters:
      iterable - the iterable. May not be null.
      predicate - the predicate. May not be null.
      Returns:
      the last element in the iterable for which the given predicate returns true, returns null if no element matches the predicate or the iterable is empty.

    • head

      public static <T> T head(Iterable<T> iterable)
      Returns the first element in the given iterable or null if empty.
      Parameters:
      iterable - the iterable. May not be null.
      Returns:
      the first element in the iterable or null.

    • tail

      public static <T> Iterable<T> tail(Iterable<T> iterable)
      Returns a view on this iterable that contains all the elements except the first.
      Parameters:
      iterable - the iterable. May not be null.
      Returns:
      an iterable with all elements except the first. Never null.
      See Also:

    • last

      @Deprecated public static <T> T last(Iterable<T> iterable)
      Deprecated.
      Use #lastOrNull(Iterable<T>) instead: in Java 21, the method getLast has been introduced to some collection classes and would be preferred to this one by the Xbase/Xtend compiler, breaking the semantics of the original code: The Java 21 getLast method throws a NoSuchElementException when the collection is empty, instead of returning null.
      Returns the last element in the given iterable or null if empty.
      Parameters:
      iterable - the iterable. May not be null.
      Returns:
      the last element in the iterable or null.

    • lastOrNull

      public static <T> T lastOrNull(Iterable<T> iterable)
      Returns the last element in the given iterable or null if empty.
      Parameters:
      iterable - the iterable. May not be null.
      Returns:
      the last element in the iterable or null.
      Since:
      2.35

    • take

      public static <T> Iterable<T> take(Iterable<T> iterable, int count)
      Returns a view on this iterable that provides at most the first count entries.
      Parameters:
      iterable - the iterable. May not be null.
      count - the number of elements that should be returned at most.
      Returns:
      an iterable with count elements. Never null.
      Throws:
      IllegalArgumentException - if count is negative.

    • drop

      @Pure public static <T> Iterable<T> drop(Iterable<T> iterable, int count)
      Returns a view on this iterable that provides all elements except the first count entries.
      Parameters:
      iterable - the iterable. May not be null.
      count - the number of elements that should be dropped.
      Returns:
      an iterable without the first count elements. Never null.
      Throws:
      IllegalArgumentException - if count is negative.

    • exists

      public static <T> boolean exists(Iterable<T> iterable, Functions.Function1<? super T,Boolean> predicate)
      Returns true if one or more elements in iterable satisfy the predicate.
      Parameters:
      iterable - the iterable. May not be null.
      predicate - the predicate. May not be null.
      Returns:
      true if one or more elements in iterable satisfy the predicate.

    • forall

      public static <T> boolean forall(Iterable<T> iterable, Functions.Function1<? super T,Boolean> predicate)
      Returns true if every element in iterable satisfies the predicate. If iterable is empty, true is returned. In other words, false is returned if at least one element fails to fulfill the predicate.
      Parameters:
      iterable - the iterable. May not be null.
      predicate - the predicate. May not be null.
      Returns:
      true if every element in iterable satisfies the predicate and also if there is no element.

    • filter

      @Pure public static <T> Iterable<T> filter(Iterable<T> unfiltered, Functions.Function1<? super T,Boolean> predicate)
      Returns the elements of unfiltered that satisfy a predicate. The resulting iterable's iterator does not support remove(). The returned iterable is a view on the original elements. Changes in the unfiltered original are reflected in the view.
      Parameters:
      unfiltered - the unfiltered iterable. May not be null.
      predicate - the predicate. May not be null.
      Returns:
      an iterable that contains only the elements that fulfill the predicate. Never null.

    • reject

      @Pure public static <T> Iterable<T> reject(Iterable<T> unfiltered, Functions.Function1<? super T,Boolean> predicate)
      Returns the elements of unfiltered that do not satisfy a predicate. The resulting iterable's iterator does not support remove(). The returned iterable is a view on the original elements. Changes in the unfiltered original are reflected in the view.
      Parameters:
      unfiltered - the unfiltered iterable. May not be null.
      predicate - the predicate. May not be null.
      Returns:
      an iterable that contains only the elements that do not fulfill the predicate. Never null.
      Since:
      2.11

    • reject

      @GwtIncompatible("Class.isInstance") @Pure public static <T> Iterable<T> reject(Iterable<T> unfiltered, Class<?> type)
      Returns the elements of unfiltered that are not instanceof type. The resulting iterable's iterator does not support remove(). The returned iterable is a view on the original elements. Changes in the unfiltered original are reflected in the view.
      Parameters:
      unfiltered - the unfiltered iterable. May not be null.
      type - the type of elements undesired. May not be null.
      Returns:
      an iterable that contains only the elements that are not instances of type. Never null. Note that the elements of the iterable can be null as null is an instance of nothing.
      Since:
      2.15

    • filter

      @GwtIncompatible("Class.isInstance") @Pure public static <T> Iterable<T> filter(Iterable<?> unfiltered, Class<T> type)
      Returns all instances of class type in unfiltered. The returned iterable has elements whose class is type or a subclass of type. The returned iterable's iterator does not support remove() . The returned iterable is a view on the original elements. Changes in the unfiltered original are reflected in the view.
      Parameters:
      unfiltered - the unfiltered iterable. May not be null.
      type - the type of elements desired
      Returns:
      an unmodifiable iterable containing all elements of the original iterable that were of the requested type. Never null.

    • filterNull

      @Pure public static <T> Iterable<T> filterNull(Iterable<T> unfiltered)
      Returns a new iterable filtering any null references.
      Parameters:
      unfiltered - the unfiltered iterable. May not be null.
      Returns:
      an unmodifiable iterable containing all elements of the original iterable without any null references. Never null.

    • map

      @Pure public static <T, R> Iterable<R> map(Iterable<T> original, Functions.Function1<? super T,? extends R> transformation)
      Returns an iterable that performs the given transformation for each element of original when requested. The mapping is done lazily. That is, subsequent iterations of the elements in the iterable will repeatedly apply the transformation.

      The returned iterable's iterator supports remove() if the provided iterator does. After a successful remove() call, original no longer contains the corresponding element.

      Parameters:
      original - the original iterable. May not be null.
      transformation - the transformation. May not be null.
      Returns:
      an iterable that provides the result of the transformation. Never null.

    • flatMap

      @Pure public static <T, R> Iterable<R> flatMap(Iterable<T> original, Functions.Function1<? super T,? extends Iterable<R>> transformation)
      Returns an iterable that performs the given transformation for each element of original when requested. The mapping is done lazily. That is, subsequent iterations of the elements in the iterable will repeatedly apply the transformation.

      The transformation maps each element to an iterable, and all resulting iterables are combined to a single iterable. Effectively a combination of map(Iterable, Functions.Function1) and flatten(Iterable) is performed.

      The returned iterable's iterator does not support remove() in contrast to map(Iterable, Functions.Function1).

      Parameters:
      original - the original iterable. May not be null.
      transformation - the transformation. May not be null and must not yield null.
      Returns:
      an iterable that provides the result of the transformation. Never null.
      Since:
      2.13

    • flatten

      public static <T> Iterable<T> flatten(Iterable<? extends Iterable<? extends T>> inputs)
      Combines multiple iterables into a single iterable. The returned iterable has an iterator that traverses the elements of each iterable in inputs. The input iterators are not polled until necessary.

      The returned iterable's iterator supports remove() when the corresponding input iterator supports it. The methods of the returned iterable may throw NullPointerException if any of the input iterators are null.

      Parameters:
      inputs - the to be flattened iterables. May not be null.
      Returns:
      an iterable that provides the concatenated values of the input elements. Never null.

    • forEach

      public static <T> void forEach(Iterable<T> iterable, Procedures.Procedure1<? super T> procedure)
      Applies procedure for each element of the given iterable.
      Parameters:
      iterable - the iterable. May not be null.
      procedure - the procedure. May not be null.

    • forEach

      public static <T> void forEach(Iterable<T> iterable, Procedures.Procedure2<? super T,? super Integer> procedure)
      Applies procedure for each element of the given iterable. The procedure takes the element and a loop counter. If the counter would overflow, Integer.MAX_VALUE is returned for all subsequent elements. The first element is at index zero.
      Parameters:
      iterable - the iterable. May not be null.
      procedure - the procedure. May not be null.
      Since:
      2.3

    • join

      public static String join(Iterable<?> iterable)
      Returns the concatenated string representation of the elements in the given iterable. No delimiter is used.
      Parameters:
      iterable - the iterable. May not be null.
      Returns:
      the string representation of the iterable's elements. Never null.
      See Also:

    • join

      public static String join(Iterable<?> iterable, CharSequence separator)
      Returns the concatenated string representation of the elements in the given iterable. The separator is used to between each pair of entries in the input. The string null is used for null entries in the input.
      Parameters:
      iterable - the iterable. May not be null.
      separator - the separator. May not be null.
      Returns:
      the string representation of the iterable's elements. Never null.
      See Also:

    • join

      public static <T> String join(Iterable<T> iterable, CharSequence separator, Functions.Function1<? super T,? extends CharSequence> function)
      Returns the concatenated string representation of the elements in the given iterable. The function is used to compute the string for each element. The separator is used to between each pair of entries in the input. The string null is used if the function yields null as the string representation for an entry.
      Parameters:
      iterable - the iterable. May not be null.
      separator - the separator. May not be null.
      function - the function that is used to compute the string representation of a single element. May not be null.
      Returns:
      the string representation of the iterable's elements. Never null.

    • join

      public static <T> String join(Iterable<T> iterable, CharSequence before, CharSequence separator, CharSequence after, Functions.Function1<? super T,? extends CharSequence> function)
      Returns the concatenated string representation of the elements in the given iterable. The function is used to compute the string for each element. The separator is used to between each pair of entries in the input. The string null is used if the function yields null as the string representation for an entry.
      Parameters:
      iterable - the iterable. May not be null.
      before - prepends the resulting string if the iterable contains at least one element. May be null which is equivalent to passing an empty string.
      separator - the separator. May be null which is equivalent to passing an empty string.
      after - appended to the resulting string if the iterable contain at least one element. May be null which is equivalent to passing an empty string.
      function - the function that is used to compute the string representation of a single element. May not be null.
      Returns:
      the string representation of the iterable's elements. Never null.

    • elementsEqual

      public static boolean elementsEqual(Iterable<?> iterable, Iterable<?> other)
      Determines whether two iterables contain equal elements in the same order. More specifically, this method returns true if iterable and other contain the same number of elements and every element of iterable is equal to the corresponding element of other.
      Parameters:
      iterable - an iterable. May not be null.
      other - an iterable. May not be null.
      Returns:
      true if the two iterables contain equal elements in the same order.

    • isNullOrEmpty

      public static boolean isNullOrEmpty(Iterable<?> iterable)
      Determines if the given iterable is null or contains no elements.
      Parameters:
      iterable - the to-be-queried iterable. May be null.
      Returns:
      true if the iterable is null or contains no elements

    • isEmpty

      public static boolean isEmpty(Iterable<?> iterable)
      Determines if the given iterable contains no elements.
      Parameters:
      iterable - the to-be-queried iterable. May not be null.
      Returns:
      true if the iterable contains no elements
      See Also:

    • size

      public static int size(Iterable<?> iterable)
      Returns the number of elements in iterable.
      Parameters:
      iterable - the iterable. May not be null.
      Returns:
      the number of elements in iterable.

    • reduce

      public static <T> T reduce(Iterable<? extends T> iterable, Functions.Function2<? super T,? super T,? extends T> function)

      Applies the combinator function to all elements of the iterable in turn.

      One of the function parameters is an element of the iterable, and the other is the result of previous application of the function. The seed of the operation is the first element in the iterable. The second value is computed by applying the function to the seed together with the second element of the iterable. The third value is computed from the previous result together with the third element and so on. In other words, the previous result of each step is taken and passed together with the next element to the combinator function.

      If the iterable is empty, null is returned.

      More formally, given an iterable [a, b, c, d] and a function f, the result of reduce is f(f(f(a, b), c), d)

      Parameters:
      iterable - the to-be-reduced iterable. May not be null.
      function - the combinator function. May not be null.
      Returns:
      the last result of the applied combinator function or null for the empty input.

    • fold

      public static <T, R> R fold(Iterable<T> iterable, R seed, Functions.Function2<? super R,? super T,? extends R> function)

      Applies the combinator function to all elements of the iterable in turn and uses seed as the start value.

      One of the function parameters is an element of the iterable, and the other is the result of previous application of the function. The seed of the operation is explicitly passed to fold. The first computed value is the result of the applied function for seed and the first element of the iterable. This intermediate result together with the second element of the iterable produced the next result and so on.

      fold is similar to reduce but allows a seed value and the combinator function may be asymmetric. It takes T and R and returns R.

      If the iterable is empty, seed is returned.

      More formally, given an iterable [a, b, c, d], a seed initial and a function f, the result of fold is f(f(f(f(initial, a), b), c), d)

      Parameters:
      iterable - the to-be-folded iterable. May not be null.
      seed - the initial value. May be null.
      function - the combinator function. May not be null.
      Returns:
      the last result of the applied combinator function or seed for the empty input.

    • toList

      @Beta public static <T> List<T> toList(Iterable<T> iterable)
      Returns a list that contains all the entries of the given iterable in the same order. If the iterable is of type List, itself is returned. Therefore an unchecked cast is performed. In all other cases, the result list is a copy of the iterable.
      Parameters:
      iterable - the iterable. May not be null.
      Returns:
      a list with the same entries as the given iterable. May be the same as the given iterable iff it implements List, otherwise a copy is returned. Never null.

    • toSet

      @Beta public static <T> Set<T> toSet(Iterable<T> iterable)
      Returns a set that contains all the unique entries of the given iterable in the order of their appearance. If the iterable is of type Set, itself is returned. Therefore an unchecked cast is performed. In all other cases, the result set is a copy of the iterable with stable order.
      Parameters:
      iterable - the iterable. May not be null.
      Returns:
      a set with the unique entries of the given iterable. May be the same as the given iterable iff it implements Set, otherwise a copy is returned. Never null.

    • toInvertedMap

      public static <K, V> Map<K,V> toInvertedMap(Iterable<? extends K> keys, Functions.Function1<? super K,V> computeValues)
      Returns a map for which the Map.values() are computed by the given function, and each key is an element in the given keys. If the iterable contains equal keys more than once, the last one will be contained in the map. The map is computed eagerly. That is, subsequent changes in the keys are not reflected by the map.
      Parameters:
      keys - the keys to use when constructing the Map. May not be null.
      computeValues - the function used to produce the values for each key. May not be null.
      Returns:
      a map mapping each entry in the given iterable to the corresponding result when evaluating the function computeValues.

    • toMap

      public static <K, V> Map<K,V> toMap(Iterable<? extends V> values, Functions.Function1<? super V,K> computeKeys)
      Returns a map for which the Map.values() are the given elements in the given order, and each key is the product of invoking a supplied function computeKeys on its corresponding value. If the function produces the same key for different values, the last one will be contained in the map.
      Parameters:
      values - the values to use when constructing the Map. May not be null.
      computeKeys - the function used to produce the key for each value. May not be null.
      Returns:
      a map mapping the result of evaluating the function keyFunction on each value in the input collection to that value

    • toMap

      public static <T, K, V> Map<K,V> toMap(Iterable<? extends T> inputs, Functions.Function1<? super T,K> computeKeys, Functions.Function1<? super T,V> computeValues)
      Returns a map for which the Map.values() are the product of invoking supplied function computeValues on input iterable elements, and each key is the product of invoking a supplied function computeKeys on same elements. If the function produces the same key for different values, the last one will be contained in the map.
      Parameters:
      inputs - the elements to use when constructing the Map. May not be null.
      computeKeys - the function used to produce the key for each value. May not be null.
      computeValues - the function used to produce the values for each key. May not be null.
      Returns:
      a map mapping the result of evaluating the functions keyFunction and computeValues on each value in the input iterator to that value

    • groupBy

      public static <K, V> Map<K,List<V>> groupBy(Iterable<? extends V> values, Functions.Function1<? super V,? extends K> computeKeys)
      Returns a map for which the Map.values() is a collection of lists, where the elements in the list will appear in the order as they appeared in the iterable. Each key is the product of invoking the supplied function computeKeys on its corresponding value. So a key of that map groups a list of values for which the function produced exactly that key.
      Parameters:
      values - the values to use when constructing the Map. May not be null.
      computeKeys - the function used to produce the key for each value. May not be null.
      Returns:
      a map mapping the result of evaluating the function keyFunction on each value in the input iterable to that value. As there can be more than one value mapped by a key, the mapping result is is a list of values.
      Since:
      2.7

    • sort

      public static <T extends Comparable<? super T>> List<T> sort(Iterable<T> iterable)
      Creates a sorted list that contains the items of the given iterable. The resulting list is in ascending order, according to the natural ordering of the elements in the iterable.
      Parameters:
      iterable - the items to be sorted. May not be null.
      Returns:
      a sorted list as a shallow copy of the given iterable.
      See Also:

    • sort

      @Deprecated public static <T> List<T> sort(Iterable<T> iterable, Comparator<? super T> comparator)
      Deprecated.
      Use sortWith(Iterable, Comparator) instead.
      This method is deprecated in favor of sortWith(Iterable, Comparator). Creates a sorted list that contains the items of the given iterable. The resulting list is sorted according to the order induced by the specified comparator.
      Parameters:
      iterable - the items to be sorted. May not be null.
      comparator - the comparator to be used. May be null to indicate that the natural ordering of the elements should be used.
      Returns:
      a sorted list as a shallow copy of the given iterable.
      See Also:

    • sortWith

      public static <T> List<T> sortWith(Iterable<T> iterable, Comparator<? super T> comparator)
      Creates a sorted list that contains the items of the given iterable. The resulting list is sorted according to the order induced by the specified comparator.
      Parameters:
      iterable - the items to be sorted. May not be null.
      comparator - the comparator to be used. May be null to indicate that the natural ordering of the elements should be used.
      Returns:
      a sorted list as a shallow copy of the given iterable.
      Since:
      2.7
      See Also:

    • sortBy

      public static <T, C extends Comparable<? super C>> List<T> sortBy(Iterable<T> iterable, Functions.Function1<? super T,C> key)
      Creates a sorted list that contains the items of the given iterable. The resulting list is sorted according to the order induced by applying a key function to each element which yields a comparable criteria.
      Parameters:
      iterable - the elements to be sorted. May not be null.
      key - the key function to-be-used. May not be null.
      Returns:
      a sorted list as a shallow copy of the given iterable.
      See Also:

    • takeWhile

      public static <T> Iterable<T> takeWhile(Iterable<? extends T> iterable, Functions.Function1<? super T,Boolean> predicate)
      Returns an Iterable containing all elements starting from the head of the source up to and excluding the first element that violates the predicate The resulting Iterable is a lazily computed view, so any modifications to the underlying Iterables will be reflected on subsequent iterations. The result's Iterator does not support Iterator.remove()
      Parameters:
      iterable - the elements from which to take. May not be null.
      predicate - the predicate which decides whether to keep taking elements. May not be null.
      Returns:
      the taken elements
      Since:
      2.7

    • dropWhile

      public static <T> Iterable<T> dropWhile(Iterable<? extends T> iterable, Functions.Function1<? super T,Boolean> predicate)
      Returns an Iterable containing all elements starting from the first element for which the drop-predicate returned false. The resulting Iterable is a lazily computed view, so any modifications to the underlying Iterables will be reflected on subsequent iterations. The result's Iterator does not support Iterator.remove()
      Parameters:
      iterable - the elements from which to drop. May not be null.
      predicate - the predicate which decides whether to keep dropping elements. May not be null.
      Returns:
      the remaining elements after dropping
      Since:
      2.7

    • indexed

      public static <A> Iterable<Pair<Integer,A>> indexed(Iterable<? extends A> iterable)
      Returns an Iterable of Pairs where the nth pair is created by taking the nth element of the source as the value its 0-based index as the key. E.g. zipWitIndex(#["a", "b", "c"]) == #[(0, "a"), (1, "b"), (2, "c")] If the index would overflow, Integer.MAX_VALUE is returned for all subsequent elements. The resulting Iterable is a lazily computed view, so any modifications to the underlying Iterable will be reflected on iteration. The result's Iterator does not support Iterator.remove()
      Parameters:
      iterable - the elements. May not be null.
      Returns:
      the zipped result
      Since:
      2.7

    • min

      public static <T extends Comparable<? super T>> T min(Iterable<T> iterable)
      Finds the minimum of the given elements according to their natural ordering. If there are several mimina, the first one will be returned.
      Parameters:
      iterable - the mutually comparable elements. May not be null.
      Returns:
      the minimum
      Throws:
      NoSuchElementException - if the iterable is empty
      Since:
      2.7

    • minBy

      public static <T, C extends Comparable<? super C>> T minBy(Iterable<T> iterable, Functions.Function1<? super T,C> compareBy)
      Finds the element that yields the minimum value when passed to compareBy. If there are several minima, the first one will be returned.
      Parameters:
      iterable - the elements to find the minimum of. May not be null.
      compareBy - a function that returns a comparable characteristic to compare the elements by. May not be null.
      Returns:
      the minimum
      Throws:
      NoSuchElementException - if the iterable is empty
      Since:
      2.7

    • min

      public static <T> T min(Iterable<T> iterable, Comparator<? super T> comparator)
      Finds the mininmum element according to comparator. If there are several minima, the first one will be returned.
      Parameters:
      iterable - the elements to find the minimum of. May not be null.
      comparator - the comparison function. May not be null.
      Returns:
      the minimum
      Throws:
      NoSuchElementException - if the iterable is empty
      Since:
      2.7

    • max

      public static <T extends Comparable<? super T>> T max(Iterable<T> iterable)
      Finds the maximum of the elements according to their natural ordering. If there are several maxima, the first one will be returned.
      Parameters:
      iterable - the mutually comparable elements. May not be null.
      Returns:
      the maximum
      Throws:
      NoSuchElementException - if the iterable is empty
      Since:
      2.7

    • maxBy

      public static <T, C extends Comparable<? super C>> T maxBy(Iterable<T> iterable, Functions.Function1<? super T,C> compareBy)
      Finds the element that yields the maximum value when passed to compareBy If there are several maxima, the first one will be returned.
      Parameters:
      iterable - the elements to find the maximum of. May not be null.
      compareBy - a function that returns a comparable characteristic to compare the elements by. May not be null.
      Returns:
      the maximum
      Throws:
      NoSuchElementException - if the iterable is empty
      Since:
      2.7

    • max

      public static <T> T max(Iterable<T> iterable, Comparator<? super T> comparator)
      Finds the maximum element according to comparator. If there are several maxima, the first one will be returned.
      Parameters:
      iterable - the elements to find the maximum of. May not be null.
      comparator - the comparison function. May not be null.
      Returns:
      the maximum
      Throws:
      NoSuchElementException - if the iterable is empty
      Since:
      2.7

    • contains

      public static boolean contains(Iterable<?> iterable, Object o)
      Returns true if this Iterable contains the specified element. More formally, returns true if and only if this Iterable contains at least one element e such that (o==null ? e==null : o.equals(e)).
      Parameters:
      iterable - the elements to test
      o - element whose presence in the Iterable is to be tested
      Returns:
      true if this Iterable contains the specified element