VOOZH about

URL: https://www.geeksforgeeks.org/java/copyonwritearrayset-retainall-method-in-java-with-example/

⇱ CopyOnWriteArraySet retainAll() method in Java with Example - GeeksforGeeks

  • Courses
  • Tutorials
  • Interview Prep

CopyOnWriteArraySet retainAll() method in Java with Example

Last Updated : 24 Dec, 2018
The retainAll() method of java.util.concurrent.CopyOnWriteArraySet class is used to retain from this set all of its elements that are contained in the specified collection. Syntax: 
public boolean retainAll(Collection c)
Parameters: This method takes collection c as a parameter containing elements to be retained from this set. Returns Value: This method returns true if this set changed as a result of the call. Exception: This method throws NullPointerException if this set contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null. Below are the examples to illustrate the retainAll() method. Example 1:
Output: 
CopyOnWriteArraySet before retainAll() operation : [1, 2, 3, 4, 5]
Collection Elements to be retained : [1, 2, 3]
CopyOnWriteArraySet after retainAll() operation : [1, 2, 3]
Example 2: For NullPointerException
Output: 
CopyOnWriteArraySet before retainAll() operation : [1, 2, 3, 4, 5]
Collection Elements to be retained : null

Trying to pass null as a specified element

Exception thrown : java.lang.NullPointerException
Comment