Package com.google.common.collect

Class LinkedHashMultiset<E>

  • All Implemented Interfaces:
    , <E>, <E>
    @GwtCompatible(serializable=true,
               emulated=true)
public final class LinkedHashMultiset<E>
extends <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 .

    Since:
    2.0
    Author:
    Kevin Bourrillion, Jared Levy
    See Also:
    Serialized Form

    • Nested Class Summary

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean E element)
      Ensures that this collection contains the specified element (optional operation).
      int E element, int occurrences)
      Adds a number of occurrences of an element to this multiset.
      boolean <? extends E> elementsToAdd)
      Adds all of the elements in the specified collection to this collection (optional operation).
      void clear()
      Removes all of the elements from this collection (optional operation).
      boolean  element)
      Returns true if this collection contains the specified element.
      int  element)
      Returns the number of occurrences of an element in this multiset (the count of the element).
      static <E> LinkedHashMultiset<E> create()
      Creates a new, empty LinkedHashMultiset using the default initial capacity.
      static <E> LinkedHashMultiset<E> create​(int distinctElements)
      Creates a new, empty LinkedHashMultiset with the specified expected number of distinct elements.
      static <E> LinkedHashMultiset<E> <? extends E> elements)
      Creates a new LinkedHashMultiset containing the specified elements.
      <E> elementSet()
      Returns the set of distinct elements contained in this multiset.
      <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  object)
      Indicates whether some other object is "equal to" this one.
      void <? super E> action)
      Runs the specified action for each distinct element in this multiset, and the number of occurrences of that element.
      int hashCode()
      Returns a hash code value for the object.
      boolean isEmpty()
      Returns true if this collection contains no elements.
      <E> iterator()
      Returns an iterator over the elements contained in this collection.
      boolean  element)
      Removes a single instance of the specified element from this collection, if it is present (optional operation).
      int  element, int occurrences)
      Removes a number of occurrences of the specified element from this multiset.
      boolean <?> elementsToRemove)
      Removes all of this collection's elements that are also contained in the specified collection (optional operation).
      boolean <?> elementsToRetain)
      Retains only the elements in this collection that are contained in the specified collection (optional operation).
      int E element, int count)
      Adds or removes the necessary occurrences of an element such that the element attains the desired count.
      boolean 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 number of elements in this collection.
      toString()
      Returns a string representation of this collection.

      • Methods inherited from class java.util.

        , ,

      • Methods inherited from class java.lang.

        , , , , , , ,

      • Methods inherited from interface java.util.

        , , , , ,

    • 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:
        - if distinctElements is negative

      • create

        public static <E> <? 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 <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

      • forEachEntry

        public void forEachEntry​(<? super E> action)
        Description copied from interface: Multiset
        Runs the specified action for each distinct element in this multiset, and the number of occurrences of that element. For some Multiset implementations, this may be more efficient than iterating over the Multiset.entrySet() either explicitly or with entrySet().forEach(action).
        Specified by:
        forEachEntry in interface Multiset<E>

      • clear

        public void clear()
        Description copied from class: 
        Removes all of the elements from this collection (optional operation). The collection will be empty after this method returns.
        Specified by:
         in interface <E>

      • size

        public int size()
        Description copied from interface: 
        Returns the number of elements in this collection. If this collection contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.
        Specified by:
         in interface <E>
        Specified by:
        size in interface Multiset<E>
        Specified by:
         in class <E>
        Returns:
        the number of elements in this collection

      • iterator

        public <E> iterator()
        Description copied from class: 
        Returns an iterator over the elements contained in this collection.
        Specified by:
         in interface <E>
        Specified by:
         in interface <E>
        Specified by:
        iterator in interface Multiset<E>
        Specified by:
         in class <E>
        Returns:
        an iterator over the elements contained in this collection

      • count

        public int count​(  element)
        Description copied from interface: Multiset
        Returns the number of occurrences of an element in this multiset (the count of the element). Note that for an -based multiset, this gives the same result as (which would presumably perform more poorly).

        Note: the utility method Iterables.frequency(java.lang.Iterable<?>, java.lang.Object) generalizes this operation; it correctly delegates to this method when dealing with a multiset, but it can also accept any other iterable type.

        Specified by:
        count in interface Multiset<E>
        Parameters:
        element - the element to count occurrences of
        Returns:
        the number of occurrences of the element in this multiset; possibly zero but never negative

      • add

        public 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>
        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:
        - if the call would result in more than occurrences of element in this multiset.

      • remove

        public int remove​(  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​( 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

      • isEmpty

        public boolean isEmpty()
        Description copied from class: 
        Returns true if this collection contains no elements.
        Specified by:
         in interface <E>
        Overrides:
         in class <E>
        Returns:
        true if this collection contains no elements

      • contains

        public boolean contains​(  element)
        Description copied from class: 
        Returns true if this collection contains the specified element. More formally, returns true if and only if this collection contains at least one element e such that Objects.equals(o, e).
        Specified by:
         in interface <E>
        Specified by:
        contains in interface Multiset<E>
        Overrides:
         in class <E>
        Parameters:
        element - element whose presence in this collection is to be tested
        Returns:
        true if this collection contains the specified element

      • add

        public final boolean add​( E element)
        Description copied from class: 
        Ensures that this collection contains the specified element (optional operation). Returns true if this collection changed as a result of the call. (Returns false if this collection does not permit duplicates and already contains the specified element.)

        Collections that support this operation may place limitations on what elements may be added to this collection. In particular, some collections will refuse to add null elements, and others will impose restrictions on the type of elements that may be added. Collection classes should clearly specify in their documentation any restrictions on what elements may be added.

        If a collection refuses to add a particular element for any reason other than that it already contains the element, it must throw an exception (rather than returning false). This preserves the invariant that a collection always contains the specified element after this call returns.

        Specified by:
         in interface <E>
        Specified by:
        add in interface Multiset<E>
        Overrides:
         in class <E>
        Parameters:
        element - element whose presence in this collection is to be ensured
        Returns:
        true if this collection changed as a result of the call

      • remove

        public final boolean remove​(  element)
        Description copied from class: 
        Removes a single instance of the specified element from this collection, if it is present (optional operation). More formally, removes an element e such that Objects.equals(o, e), if this collection contains one or more such elements. Returns true if this collection contained the specified element (or equivalently, if this collection changed as a result of the call).
        Specified by:
         in interface <E>
        Specified by:
        remove in interface Multiset<E>
        Overrides:
         in class <E>
        Parameters:
        element - element to be removed from this collection, if present
        Returns:
        true if an element was removed as a result of this call

      • setCount

        public 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>
        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.

      • addAll

        public final boolean addAll​(<? extends E> elementsToAdd)
        Adds all of the elements in the specified collection to this collection (optional operation). The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. (This implies that the behavior of this call is undefined if the specified collection is this collection, and this collection is nonempty.)

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

        Specified by:
         in interface <E>
        Overrides:
         in class <E>
        Parameters:
        elementsToAdd - collection containing elements to be added to this collection
        Returns:
        true if this collection changed as a result of the call
        See Also:

      • removeAll

        public final boolean removeAll​(<?> elementsToRemove)
        Description copied from class: 
        Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection.
        Specified by:
         in interface <E>
        Specified by:
        removeAll in interface Multiset<E>
        Overrides:
         in class <E>
        Parameters:
        elementsToRemove - collection containing elements to be removed from this collection
        Returns:
        true if this collection changed as a result of the call
        See Also:
        ,

      • retainAll

        public final boolean retainAll​(<?> elementsToRetain)
        Description copied from class: 
        Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection.
        Specified by:
         in interface <E>
        Specified by:
        retainAll in interface Multiset<E>
        Overrides:
         in class <E>
        Parameters:
        elementsToRetain - collection containing elements to be retained in this collection
        Returns:
        true if this collection changed as a result of the call
        See Also:
        ,

      • elementSet

        public <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 final boolean equals​(  object)
        Indicates whether some other object is "equal to" this one.

        The equals method implements an equivalence relation on non-null object references:

        • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
        • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
        • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
        • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
        • For any non-null reference value x, x.equals(null) should return false.

        The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

        Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

        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:
         in interface <E>
        Specified by:
        equals in interface Multiset<E>
        Overrides:
         in class 
        Parameters:
        object - the reference object with which to compare.
        Returns:
        true if this object is the same as the obj argument; false otherwise.
        See Also:
        ,

      • hashCode

        public final int hashCode()
        Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by .

        The general contract of hashCode is:

        • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
        • If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
        • It is not required that if two objects are unequal according to the method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

        As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.)

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

        Specified by:
         in interface <E>
        Specified by:
        hashCode in interface Multiset<E>
        Overrides:
         in class 
        Returns:
        a hash code value for this object.
        See Also:
        ,

      • toString

        public final  toString()
        Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters ", " (comma and space). Elements are converted to strings as by .

        This implementation returns the result of invoking toString on Multiset.entrySet().

        Specified by:
        toString in interface Multiset<E>
        Overrides:
         in class <E>
        Returns:
        a string representation of this collection