Java中的 ConcurrentSkipListSet 示例

Java中的ConcurrentSkipListSet类是Java Collection Framework 的一部分，实现了Collection 接口和AbstractSet 类。它在Java中提供了可扩展和并发的 NavigableSet 版本。 ConcurrentSkipListSet 的实现基于ConcurrentSkipListMap 。 ConcurrentSkipListSet 中的元素默认按其自然顺序或在集合创建时提供的 Comparator 排序，具体取决于使用的构造函数。

由于它实现了SortedSet和NavigableSet ，因此它与 TreeSet 类似，但多了一个并发特性。由于它是线程安全的，它可以被多个线程同时使用，而 TreeSet 不是线程安全的。

类层次结构：

宣言：

public class ConcurrentSkipListSet
    extends AbstractSet
        implements NavigableSet, Cloneable, Serializable

Where E is the type of elements maintained by this collection

ConcurrentSkipListSet 的一些要点：

• 它实现了 Serializable 、 Cloneable 、 Iterable 、 Collection 、 NavigableSet 、 Set 、 SortedSet 接口。
• 它不允许空元素，因为空参数和返回值无法可靠地区分不存在元素。
• 它的实现为包含、添加和删除操作及其变体提供了平均 log(n) 时间成本。
• 它是线程安全的。
• 当需要同时修改 set 时，应该优先于实现 Set 接口。

构造函数：

1. ConcurrentSkipListSet() ：该构造函数用于构造一个空集。

ConcurrentSkipListSet set = new ConcurrentSkipListSet();

2. ConcurrentSkipListSet(Collection c) ：该构造函数用于构造一个集合，该集合的元素作为参数传递。

ConcurrentSkipListSet set = new ConcurrentSkipListSet(Collection c);

3. ConcurrentSkipListSet(Comparatorcomparator) ：此构造函数用于构造一个新的空集合，该集合根据指定的比较器对其元素进行排序。

ConcurrentSkipListSet set = new ConcurrentSkipListSet(Comparator comparator);

4. ConcurrentSkipListSet(SortedSet s) ：该构造函数用于构造一个新集合，该集合包含与指定排序集合相同的元素并使用相同的顺序。

ConcurrentSkipListSet set = new ConcurrentSkipListSet(SortedSet s);

示例 1：

Java

// Java program to demonstrate ConcurrentSkipListSet
  
import java.util.*;
import java.util.concurrent.ConcurrentSkipListSet;
  
class ConcurrentSkipListSetLastExample1 {
    public static void main(String[] args)
    {
  
        // Initializing the set using
        // ConcurrentSkipListSet()
        ConcurrentSkipListSet set
            = new ConcurrentSkipListSet();
  
        // Adding elements to this set
        set.add(78);
        set.add(64);
        set.add(12);
        set.add(45);
        set.add(8);
  
        // Printing the ConcurrentSkipListSet
        System.out.println("ConcurrentSkipListSet: " + set);
  
        // Initializing the set using
        // ConcurrentSkipListSet(Collection)
        ConcurrentSkipListSet set1
            = new ConcurrentSkipListSet(set);
  
        // Printing the ConcurrentSkipListSet1
        System.out.println("ConcurrentSkipListSet1: "
                           + set1);
  
        // Initializing the set using
        // ConcurrentSkipListSet()
        ConcurrentSkipListSet set2
            = new ConcurrentSkipListSet<>();
  
        // Adding elements to this set
        set2.add("Apple");
        set2.add("Lemon");
        set2.add("Banana");
        set2.add("Apple");
  
        // creating an iterator
        Iterator itr = set2.iterator();
  
        System.out.print("Fruits Set: ");
        while (itr.hasNext()) {
            System.out.print(itr.next() + " ");
        }
    }
}

输出：

ConcurrentSkipListSet: [8, 12, 45, 64, 78]
ConcurrentSkipListSet1: [8, 12, 45, 64, 78]
Fruits Set: Apple Banana Lemon 

示例 2：

Java

// Java program to demonstrate ConcurrentSkipListSet
  
import java.util.concurrent.ConcurrentSkipListSet;
  
class ConcurrentSkipListSetLastExample1 {
    
    public static void main(String[] args)
    {
  
        // Initializing the set using ConcurrentSkipListSet()
        ConcurrentSkipListSet
            set = new ConcurrentSkipListSet();
  
        // Adding elements to this set
        // using add() method
        set.add(78);
        set.add(64);
        set.add(12);
        set.add(45);
        set.add(8);
  
        // Printing the ConcurrentSkipListSet
        System.out.println("ConcurrentSkipListSet: "
                           + set);
  
        // Printing the highest element of the set
        // using last() method
        System.out.println("The highest element of the set: "
                           + set.last());
  
        // Retrieving and removing first element of the set
        System.out.println("The first element of the set: "
                           + set.pollFirst());
  
        // Checks if 9 is present in the set
        // using contains() method
        if (set.contains(9))
            System.out.println("9 is present in the set.");
        else
            System.out.println("9 is not present in the set.");
  
        // Printing the size of the set
        // using size() method
        System.out.println("Number of elements in the set = "
                           + set.size());
    }
}

输出：

ConcurrentSkipListSet: [8, 12, 45, 64, 78]
The highest element of the set: 78
The first element of the set: 8
9 is not present in the set.
Number of elements in the set = 4

ConcurrentSkipListSet 的方法

METHOD	DESCRIPTION
add(E e)	Adds the specified element to this set if it is not already present.
ceiling(E e)	Returns the least element in this set greater than or equal to the given element, or null if there is no such element.
clear()	Removes all of the elements from this set.
clone()	Returns a shallow copy of this ConcurrentSkipListSet instance.
comparator()	Returns the comparator used to order the elements in this set, or null if this set uses the natural ordering of its elements.
contains(Object o)	Returns true if this set contains the specified element.
descendingIterator()	Returns an iterator over the elements in this set in descending order.
descendingSet()	Returns a reverse order view of the elements contained in this set.
equals(Object o)	Compares the specified object with this set for equality.
first()	Returns the first (lowest) element currently in this set.
floor(E e)	Returns the greatest element in this set less than or equal to the given element, or null if there is no such element.
headSet(E toElement)	Returns a view of the portion of this set whose elements are strictly less than toElement.
headSet(E toElement, boolean inclusive)	Returns a view of the portion of this set whose elements are less than (or equal to, if inclusive is true) toElement.
higher(E e)	Returns the least element in this set strictly greater than the given element, or null if there is no such element.
isEmpty()	Returns an iterator over the elements in this set in ascending order.
last()	Returns the last (highest) element currently in this set.
lower(E e)	Returns the greatest element in this set strictly less than the given element, or null if there is no such element.
pollFirst()	Retrieves and removes the first (lowest) element, or returns null if this set is empty.
pollLast()	Retrieves and removes the last (highest) element, or returns null if this set is empty.
remove(Object o)	Removes the specified element from this set if it is present.
removeAll(Collection c)	Removes from this set all of its elements that are contained in the specified collection.
size()	Returns the number of elements in this set.
spliterator()	Returns a Spliterator over the elements in this set.
subSet(E fromElement, boolean  fromInclusive, E toElement, boolean toInclusive)	Returns a view of the portion of this set whose elements range from fromElement to toElement.
subSet(E fromElement, E toElement)	Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive.
tailSet(E fromElement)	Returns a view of the portion of this set whose elements are greater than or equal to fromElement.
tailSet(E fromElement, boolean inclusive)	Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement.

从类Java.util.AbstractSet 继承的方法

METHOD	DESCRIPTION
hashCode()	Returns the hash code value for this set.

从类Java.util.AbstractCollection 继承的方法

METHOD	DESCRIPTION
addAll(Collection c)	Adds all of the elements in the specified collection to this collection (optional operation).
containsAll(Collection c)	Returns true if this collection contains all of the elements in the specified collection.
retainAll(Collection c)	Retains only the elements in this collection that are contained in the specified collection (optional operation).
toArray()	Returns an array containing all of the elements in this collection.
toArray(T[] a)	Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
toString()	Returns a string representation of this collection.

从接口Java.util.Set 继承的方法

METHOD	DESCRIPTION
addAll(Collection c)	Adds all of the elements in the specified collection to this set if they’re not already present (optional operation).
containsAll(Collection c)	Returns true if this set contains all of the elements of the specified collection.
hashCode()	Returns the hash code value for this set.
retainAll(Collection c)	Retains only the elements in this set that are contained in the specified collection (optional operation).
toArray()	Returns an array containing all of the elements in this set.
toArray(T[] a)	Returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array.

从接口Java.util.Collection 继承的方法

METHOD	DESCRIPTION
parallelStream()	Returns a possibly parallel Stream with this collection as its source.
removeIf(Predicate filter)	Removes all of the elements of this collection that satisfy the given predicate.
stream()	Returns a sequential Stream with this collection as its source.

从接口Java.lang.Iterable 继承的方法

METHOD	DESCRIPTION
forEach(Consumer action)	Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.