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Java Vector retainAll() Method with Example

Vector Class retainAll() method: Here, we are going to learn about the retainAll() method of Vector Class with its syntax and example.
Submitted by Preeti Jain, on March 19, 2020

Vector Class retainAll() method

• retainAll() method is available in java.util package.
• retainAll() method is used to retain all those elements of this Vector that exists in the given Collection.
• retainAll() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• retainAll() method may throw an exception at the time of retaining element.
  NullPointerException: This exception may throw when the given parameter is null exists.

Syntax:

    public boolean retainAll(Collection co);

Parameter(s):

• Collection co – represents the collection object that is to be retained in this Vector.

Return value:

The return type of the method is boolean, it returns true when element exists in the given collection is to be retained in this vector otherwise it returns false.

Example:

// Java program to demonstrate the example 
// of boolean retainAll(Collection co) method 
// of Vector 

import java.util.*;

public class RetainAllOfVector {
 public static void main(String[] args) {
  // Instantiates a Vector object  with
  // initial capacity of "10"
  Vector < String > v = new Vector < String > (10);
  ArrayList arr_l = new ArrayList();

  // By using add() method is to add the
  // elements in this v
  v.add("C");
  v.add("C++");
  v.add("JAVA");

  // By using add() method is to add the
  // elements in this arr_l
  arr_l.add("C");
  arr_l.add("C++");
  arr_l.add("SFDC");

  // Display Vector and ArrayList
  System.out.println("v: " + v);
  System.out.println("arr_l: " + arr_l);

  // By using retainAll(arr_l) method is to
  // retain all elements of this vector v that
  // exists in the given collection arr_l
  v.retainAll(arr_l);

  // Display updated Vector
  System.out.println("v.retainAll(arr_l): " + v);
 }
}

Output

v: [C, C++, JAVA]
arr_l: [C, C++, SFDC]
v.retainAll(arr_l): [C, C++]