What is the CopyOnWriteArraySet.contains method in Java?

CopyOnWriteArraySet is a thread-safe version of SetA collection that contains no duplicate elements. It internally uses CopyOnWriteArrayList for its operations. For all the write operations like add or set, it makes a fresh copy of the underlying array and operates on the cloned array. Read more about CopyOnWriteArraySet here.

The contains method is used to check if an element is present in the CopyOnWriteArraySet object.

Syntax

public boolean contains(Object o)

Parameter

This method takes the element to be checked for presence as a parameter.

Return value

This method returns true if the passed element is present in the set. Otherwise, it returns false.

Code

The code below demonstrates how to use the contains method.

import java.util.concurrent.CopyOnWriteArraySet;
class Contains {
    public static void main( String args[] ) {
      CopyOnWriteArraySet<String> set = new CopyOnWriteArraySet<>();
      set.add("1");
      set.add("2");
      set.add("3");
      System.out.println("The set is " + set);
      
      System.out.println("Check if 1 present in the set : " + set.contains("1"));
      System.out.println("Check if 4 present in the set : " + set.contains("4"));
    }
}

Explanation

In the code above,

  • In line 1, we import the CopyOnWriteArraySet class.

  • In line 4, we create a CopyOnWriteArraySet object with the name set.

  • In lines 5-7, we use the add method of the set object to add three elements ("1","2","3") to the set.

  • In line 10, we use the contains method of the set object to check if the element "1" is present in the set. We get true as a result.

  • In line 11, we use the contains method to check if the element "4" is present in the set. We get false as a result, because "4" is not present in the set.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)