Java Collections Framework- CopyOnWriteArraySet class� 

The CopyOnWriteArraySet class implements the Serilizable, Iterable, Collection, Set interfaces. For all of the CopyOnWriteArraySet operations

Java Collections Framework- CopyOnWriteArraySet class 

The CopyOnWriteArraySet class implements the Serilizable, Iterable<E>, Collection<E>, Set<E> interfaces. For all of the CopyOnWriteArraySet operations a Set uses an inner CopyOnWriteArrayList. This class is best suited for applications where the set contains only a few elements and where read-only operations greatly outnumber writes and there is a need to you to prevent the interference among threads during traversal. This class is a Thread-safe. In this class Iterator traverses fast and cannot be obstructed from the other threads. 

This class is a member of Java Collection Framework.

The CopyOnWriteArraySet class have two constructor.

CopyOnWriteArraySet() : This constructor makes an empty set.

CopyOnWriteArraySet(Collection c) : This constructor makes a set that keeps all of the elements of a particular collection.

Syntax 

public class CopyOnWriteArraySet<E>

Parameter description

E : It is the type of element that is held by this collection.

Methods of CopyOnWriteArraySet are :

• boolean add(E e)
• boolean addAll(Collection<? extends E> c)
• void clear()
• boolean contains(Object o)
• boolean containsAll(Collection<?> c)
• boolean equals(Object o)
• boolean isEmpty()
• Iterator<E> iterator()
• boolean remove(Object o)
• boolean removeAll(Collection<?> c)
• boolean retainAll(Collection<?> c)
• int size()
• Object[] toArray()
• <T> T[] toArray(T[] a)

Example :

Here we will discuss an example in which some methods of this class are implemented.

package devmanuals.com;
import java.util.List;
import java.util.ArrayList;
import java.util.concurrent.*;
import java.util.Set;
import java.util.Iterator;
public class CopyOnWriteArraySetDemo {
  public static void main(String args[]) {
    CopyOnWriteArraySet set = new CopyOnWriteArraySet();
    set.add("A");
    set.add("B");
    set.add("C");
    set.add("D");
    set.add("E");
    set.add("F");
    System.out.println("Elements of set = " + set);
    Set s = new ConcurrentSkipListSet();
    s.add(1);
    s.add(2);
    s.add(3);
    s.add(4);
    s.add(5);
    s.add(6);
    // addAll() method
    boolean bol = set.addAll(s);
    System.out.println("Elements after adding all the elements into one set = "+ set);
    // contains() method
    boolean bol1 = s.contains(6);
    System.out.println("Does set 's' contains '6' : " + bol1);
    // containsAll() method
    boolean bol2 = set.containsAll(s);
    System.out.println("Does Set 'set' contains the elements of Set 's' : "+ bol2);
    // equals() method
    boolean bol3 = set.equals(s);
    System.out.println("Are the elements of Set 's' and 'set' equals : "+ bol3);
    // isEmpty() method
    boolean bol4 = set.isEmpty();
    System.out.println("Set 'set' is empty : " + bol4);
    // iterator() method
    Iterator itr = set.iterator();
    System.out.println("Elements of set =");
    while (itr.hasNext()) {
      System.out.println(itr.next());
    }
    // size() method
    Integer it = set.size();
    System.out.println("Size of set = " + it);
    // remove(0) method
    boolean bol5 = s.remove(4);
    System.out.println("Did the element remove from set 's' : " + bol5);
    // clear() method
    s.clear();
    System.out.println("Elements of the set 's' : " + s);
  }
}

Output :

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