Package com.google.common.collect

Class HashMultiset<E extends @Nullable Object>

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean add​(E element)
      Adds a single occurrence of the specified element to this multiset.
      int add​(E element, int occurrences)
      Adds a number of occurrences of an element to this multiset.
      boolean addAll​(Collection<? extends E> elementsToAdd)
      void clear()  
      boolean contains​(Object element)
      Determines whether this multiset contains the specified element.
      int count​(Object element)
      Returns the number of occurrences of an element in this multiset (the count of the element).
      static <E extends @Nullable Object>
      HashMultiset<E>      		 create()
      Creates a new, empty HashMultiset using the default initial capacity.
      static <E extends @Nullable Object>
      HashMultiset<E>      		 create​(int distinctElements)
      Creates a new, empty HashMultiset with the specified expected number of distinct elements.
      static <E extends @Nullable Object>
      HashMultiset<E>      		 create​(Iterable<? extends E> elements)
      Creates a new HashMultiset containing the specified elements.
      Set<E> elementSet()
      Returns the set of distinct elements contained in this multiset.
      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.
      boolean equals​(Object object)
      Compares the specified object with this multiset for equality.
      int hashCode()
      Returns the hash code for this multiset.
      boolean isEmpty()  
      Iterator<E> iterator()
      boolean remove​(Object element)
      Removes a single occurrence of the specified element from this multiset, if present.
      int remove​(Object element, int occurrences)
      Removes a number of occurrences of the specified element from this multiset.
      boolean removeAll​(Collection<?> elementsToRemove)
      boolean retainAll​(Collection<?> elementsToRetain)
      int setCount​(E element, int count)
      Adds or removes the necessary occurrences of an element such that the element attains the desired count.
      boolean setCount​(E element, int oldCount, int newCount)
      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.
      int size()
      Returns the total number of all occurrences of all elements in this multiset.
      String toString()

    • Method Detail

      • create

        public static <E extends @Nullable Object> HashMultiset<E> create​(int distinctElements)
        Creates a new, empty HashMultiset 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 extends @Nullable Object> HashMultiset<E> create​(Iterable<? extends E> elements)
        Creates a new HashMultiset containing the specified elements.

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

        Parameters:
        elements - the elements that the multiset should contain

      • add

        @CanIgnoreReturnValue
public final int add​(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 extends @Nullable Object>
        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

        @CanIgnoreReturnValue
public final int remove​(@CheckForNull
                        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 extends @Nullable Object>
        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

        @CanIgnoreReturnValue
public final int setCount​(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 extends @Nullable Object>
        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

      • setCount

        public final boolean setCount​(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 extends @Nullable Object>
        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.

      • add

        @CanIgnoreReturnValue
public final boolean add​(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.

        To both add the element and obtain the previous count of that element, use add(element, 1) instead.

        Specified by:
        add in interface Collection<E extends @Nullable Object>
        Specified by:
        add in interface Multiset<E extends @Nullable Object>
        Overrides:
        add in class AbstractCollection<E extends @Nullable Object>
        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

      • 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 extends @Nullable Object>
        Returns:
        a view of the set of distinct elements in this multiset

      • entrySet

        public Set<Multiset.Entry<E>> entrySet()
        Description copied from interface: Multiset
        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.

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

      • equals

        public final boolean equals​(@CheckForNull
                            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 extends @Nullable Object>
        Specified by:
        equals in interface Multiset<E extends @Nullable Object>
        Overrides:
        equals in class Object

      • hashCode

        public final 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 extends @Nullable Object>
        Specified by:
        hashCode in interface Multiset<E extends @Nullable Object>
        Overrides:
        hashCode in class Object