Package com.google.common.collect

Class LinkedHashMultiset<E>

  • All Implemented Interfaces:
    Multiset<E>, Serializable, Iterable<E>, Collection<E>
    @GwtCompatible(serializable=true,
               emulated=true)
public final class LinkedHashMultiset<E>
extends AbstractCollection<E>
    A Multiset implementation with predictable iteration order. Its iterator orders elements according to when the first occurrence of the element was added. When the multiset contains multiple instances of an element, those instances are consecutive in the iteration order. If all occurrences of an element are removed, after which that element is added to the multiset, the element will appear at the end of the iteration.

    See the Guava User Guide article on Multiset.

    Since:
    2.0 (imported from Google Collections Library)
    See Also:
    Serialized Form

    • Method Detail

      • create

        public static <E> LinkedHashMultiset<E> create()
        Creates a new, empty LinkedHashMultiset using the default initial capacity.

      • create

        public static <E> LinkedHashMultiset<E> create​(int distinctElements)
        Creates a new, empty LinkedHashMultiset with the specified expected number of distinct elements.
        Parameters:
        distinctElements - the expected number of distinct elements
        Throws:
        IllegalArgumentException - if distinctElements is negative

      • create

        public static <E> LinkedHashMultiset<E> create​(Iterable<? extends E> elements)
        Creates a new LinkedHashMultiset containing the specified elements.

        This implementation is highly efficient when elements is itself a Multiset.

        Parameters:
        elements - the elements that the multiset should contain

      • entrySet

        public Set<Multiset.Entry<E>> entrySet()
        Returns a view of the contents of this multiset, grouped into Multiset.Entry instances, each providing an element of the multiset and the count of that element. This set contains exactly one entry for each distinct element in the multiset (thus it always has the same size as the Multiset.elementSet()). The order of the elements in the element set is unspecified.

        The entry set is backed by the same data as the multiset, so any change to either is immediately reflected in the other. However, multiset changes may or may not be reflected in any Entry instances already retrieved from the entry set (this is implementation-dependent). Furthermore, implementations are not required to support modifications to the entry set at all, and the Entry instances themselves don't even have methods for modification. See the specific implementation class for more details on how its entry set handles modifications.

        Invoking Multiset.Entry.getCount() on an entry in the returned set always returns the current count of that element in the multiset, as opposed to the count at the time the entry was retrieved.

        Specified by:
        entrySet in interface Multiset<E>
        Returns:
        a set of entries representing the data of this multiset

      • clear

        public void clear()
        Specified by:
        clear in interface Collection<E>

      • size

        public int size()
        Specified by:
        size in interface Collection<E>

      • iterator

        public Iterator<E> iterator()
        Description copied from interface: Multiset

        Elements that occur multiple times in the multiset will appear multiple times in this iterator, though not necessarily sequentially.

        Specified by:
        iterator in interface Collection<E>
        Specified by:
        iterator in interface Iterable<E>
        Specified by:
        iterator in interface Multiset<E>

      • add

        public int add​(@Nullable
               E element,
               int occurrences)
        Adds a number of occurrences of an element to this multiset. Note that if occurrences == 1, this method has the identical effect to Multiset.add(Object). This method is functionally equivalent (except in the case of overflow) to the call addAll(Collections.nCopies(element, occurrences)), which would presumably perform much more poorly.
        Specified by:
        add in interface Multiset<E>
        Parameters:
        element - the element to add occurrences of; may be null only if explicitly allowed by the implementation
        occurrences - the number of occurrences of the element to add. May be zero, in which case no change will be made.
        Returns:
        the count of the element before the operation; possibly zero
        Throws:
        IllegalArgumentException - if the call would result in more than Integer.MAX_VALUE occurrences of element in this multiset.

      • remove

        public int remove​(@Nullable
                  Object element,
                  int occurrences)
        Description copied from interface: Multiset
        Removes a number of occurrences of the specified element from this multiset. If the multiset contains fewer than this number of occurrences to begin with, all occurrences will be removed. Note that if occurrences == 1, this is functionally equivalent to the call remove(element).
        Specified by:
        remove in interface Multiset<E>
        Parameters:
        element - the element to conditionally remove occurrences of
        occurrences - the number of occurrences of the element to remove. May be zero, in which case no change will be made.
        Returns:
        the count of the element before the operation; possibly zero

      • setCount

        public int setCount​(@Nullable
                    E element,
                    int count)
        Description copied from interface: Multiset
        Adds or removes the necessary occurrences of an element such that the element attains the desired count.
        Specified by:
        setCount in interface Multiset<E>
        Parameters:
        element - the element to add or remove occurrences of; may be null only if explicitly allowed by the implementation
        count - the desired count of the element in this multiset
        Returns:
        the count of the element before the operation; possibly zero

      • contains

        public boolean contains​(@Nullable
                        Object element)
        Description copied from interface: Multiset
        Determines whether this multiset contains the specified element.

        This method refines Collection.contains(java.lang.Object) to further specify that it may not throw an exception in response to element being null or of the wrong type.

        Specified by:
        contains in interface Collection<E>
        Specified by:
        contains in interface Multiset<E>
        Overrides:
        contains in class AbstractCollection<E>
        Parameters:
        element - the element to check for
        Returns:
        true if this multiset contains at least one occurrence of the element

      • add

        public boolean add​(@Nullable
                   E element)
        Description copied from interface: Multiset
        Adds a single occurrence of the specified element to this multiset.

        This method refines Collection.add(E), which only ensures the presence of the element, to further specify that a successful call must always increment the count of the element, and the overall size of the collection, by one.

        Specified by:
        add in interface Collection<E>
        Specified by:
        add in interface Multiset<E>
        Overrides:
        add in class AbstractCollection<E>
        Parameters:
        element - the element to add one occurrence of; may be null only if explicitly allowed by the implementation
        Returns:
        true always, since this call is required to modify the multiset, unlike other Collection types

      • remove

        public boolean remove​(@Nullable
                      Object element)
        Description copied from interface: Multiset
        Removes a single occurrence of the specified element from this multiset, if present.

        This method refines Collection.remove(java.lang.Object) to further specify that it may not throw an exception in response to element being null or of the wrong type.

        Specified by:
        remove in interface Collection<E>
        Specified by:
        remove in interface Multiset<E>
        Overrides:
        remove in class AbstractCollection<E>
        Parameters:
        element - the element to remove one occurrence of
        Returns:
        true if an occurrence was found and removed

      • setCount

        public boolean setCount​(@Nullable
                        E element,
                        int oldCount,
                        int newCount)
        Description copied from interface: Multiset
        Conditionally sets the count of an element to a new value, as described in Multiset.setCount(Object, int), provided that the element has the expected current count. If the current count is not oldCount, no change is made.
        Specified by:
        setCount in interface Multiset<E>
        Parameters:
        element - the element to conditionally set the count of; may be null only if explicitly allowed by the implementation
        oldCount - the expected present count of the element in this multiset
        newCount - the desired count of the element in this multiset
        Returns:
        true if the condition for modification was met. This implies that the multiset was indeed modified, unless oldCount == newCount.

      • elementSet

        public Set<E> elementSet()
        Description copied from interface: Multiset
        Returns the set of distinct elements contained in this multiset. The element set is backed by the same data as the multiset, so any change to either is immediately reflected in the other. The order of the elements in the element set is unspecified.

        If the element set supports any removal operations, these necessarily cause all occurrences of the removed element(s) to be removed from the multiset. Implementations are not expected to support the add operations, although this is possible.

        A common use for the element set is to find the number of distinct elements in the multiset: elementSet().size().

        Specified by:
        elementSet in interface Multiset<E>
        Returns:
        a view of the set of distinct elements in this multiset

      • equals

        public boolean equals​(@Nullable
                      Object object)
        Compares the specified object with this multiset for equality. Returns true if the given object is also a multiset and contains equal elements with equal counts, regardless of order.

        This implementation returns true if object is a multiset of the same size and if, for each element, the two multisets have the same count.

        Specified by:
        equals in interface Collection<E>
        Specified by:
        equals in interface Multiset<E>
        Overrides:
        equals in class Object

      • hashCode

        public int hashCode()
        Returns the hash code for this multiset. This is defined as the sum of 
           

   ((element == null) ? 0 : element.hashCode()) ^ count(element)

        over all distinct elements in the multiset. It follows that a multiset and its entry set always have the same hash code.

        This implementation returns the hash code of Multiset.entrySet().

        Specified by:
        hashCode in interface Collection<E>
        Specified by:
        hashCode in interface Multiset<E>
        Overrides:
        hashCode in class Object