Guava new collection type

        Guava Introduced a lot of JDK There is no the , but New collection types that are obviously useful , These new types are for and JDK Set framework coexists , Instead of going to JDK Other concepts are hard plugged in the set abstraction

• Multiset

  • Set up set and list Characteristics of : Elements can be repeated , Element disorder ( Having no element order restrictions ArrayList<E>)

/**
 * @author nieyapeng
 * @create 2022-02-06-20:20
 *
 * Multiset
 *       Set up set and list Characteristics of : Elements can be repeated , Element disorder ( Having no element order restrictions ArrayList<E>)
 *      add(E) Add a single given element 
 *      iterator() Returns an iterator , contain Multiset All elements of （ Including elements of repetition ）
 *      size() Returns the total number of all elements （ Including elements of repetition ）
 *
 *
 *  When put  Multiset regard as Map<E, Integer> when , It also provides query operations that meet performance expectations ：
 *      count(Object) Returns the count of the given element .HashMultiset.count The complexity of is O(1),TreeMultiset.count The complexity of is O(log n).
 *      entrySet() return Set<Multiset.Entry<E>>, and Map Of entrySet similar .
 *      elementSet() Returns all the Set<E>, and Map Of keySet() similar .
 *       all Multiset The memory consumption of the implementation increases linearly with the number of non repeating elements .
 *
 *
 * Multiset No Map
 *       Please note that ,Multiset<E> No Map<E, Integer>, although Map Maybe some Multiset Part of the implementation . To be precise Multiset It's a kind of Collection type , And fulfilled Collection Interface related contracts . About Multiset and Map The other notable differences are ：
 *      Multiset The element count in can only be positive . The count of any element cannot be negative , Nor is 0.elementSet() and entrySet() There will be no such element in the view .
 *      multiset.size() Returns the size of the collection , Equal to the sum of all element counts . For the number of non repeating elements , You should use elementSet().size() Method .（ therefore ,add(E) hold multiset.size() increase 1）
 *      multiset.iterator() Will iterate over the repeating elements , So the iteration length is equal to multiset.size().
 *      Multiset Support direct addition 、 Reduce or set the count of elements .setCount(elem, 0) Equivalent to removing all elem.
 *       Yes multiset  Elements not in ,multiset.count(elem) Always return 0.
 *
 *
 *       Map	                   Corresponding Multiset	           Do you support null Elements 
 *       HashMap	              HashMultiset	               yes 
 *       TreeMap	              TreeMultiset	               yes （ If comparator Words of support ）
 *       LinkedHashMap	          LinkedHashMultiset	       yes 
 *       ConcurrentHashMap	      ConcurrentHashMultiset	   no 
 *       ImmutableMap	          ImmutableMultiset	           no 
 */
public class MultiSetDemo {
    public static void main(String[] args) {
        HashMultiset<String> hashMultiset = HashMultiset.create();
        //add(E) Add a single given element 
        hashMultiset.add("nieyp");
        hashMultiset.add("nieyp");
        hashMultiset.add("nieyp1");
        hashMultiset.add("nieyp1");
        hashMultiset.add("nieyp11");
        //count(Object) Returns the count of the given element .HashMultiset.count The complexity of is O(1),TreeMultiset.count The complexity of is O(log n).
        int count = hashMultiset.count("nieyp");
        System.out.println("nieyp Number of occurrences "+count);
        /*iterator() Returns an iterator , contain Multiset All elements of （ Including elements of repetition ）
            nieyp11
            nieyp1
            nieyp1
            nieyp
            nieyp
        */
        Iterator<String> iterable = hashMultiset.iterator();
        while (iterable.hasNext()){
            String result = iterable.next();
            System.out.println(result);
        }
        //size() Returns the total number of all elements （ Including elements of repetition ）
        int size = hashMultiset.size();
        System.out.println(size);

        //entrySet() return Set<Multiset.Entry<E>>, and Map Of entrySet similar .[nieyp11, nieyp1 x 2, nieyp x 2]
        Set<Multiset.Entry<String>> entrySet = hashMultiset.entrySet();
        for (Multiset.Entry<String> stringEntry : entrySet) {
            System.out.println(stringEntry);
        }
        System.out.println(entrySet);
        // elementSet() Returns all the Set<E>, and Map Of keySet() similar .[nieyp11, nieyp1, nieyp]
        Set<String> set = hashMultiset.elementSet();
        System.out.println(set);
    }
}