The retainAll method of class vector in java is an inbuilt function in Java which is used to retains only the elements in this Vector that are contained in the specified Collection. In other words, removes from this Vector all of its elements that are not contained in the specified Collection.
Syntax:
public boolean retainAll(Collection c)
Parameter: Here c is a collection of elements to be retained in this Vector (all other elements are removed).
Return value: This method will return a boolean value, i.e true if this Vector changed as a result of the call or else false.
Exception: This method will throw the following exceptions.
Below programs illustrate the Vector.retainAll() method in Java:
Program 1:To illustrate Vector.retainAll() method in Java.
import java.util.*;import java.io.*;public class GFG {    public static void main(String args[])    {        // Creating an empty Vector        Vector<String> v1 = new Vector<String>();          // adding elements to the vector v1        v1.add("Geeks");        v1.add("For");        v1.add("Geeks");        v1.add("is");        v1.add("a");        v1.add("computer");        v1.add("science");        v1.add("portal");          System.out.println("Elements of vector1:" + v1);          // Creating an other empty vector        Vector<String> v2 = new Vector<String>();          // adding elements to the vector v2        v2.add("Geeks");        v2.add("For");        v2.add("Geeks");        v2.add("contains");        v2.add("well");        v2.add("written");        v2.add("programming");        v2.add("articles");        v2.add("and");        v2.add("much");        v2.add("more.");          System.out.println("Elements of vector2:" + v2);          System.out.println("Calling retainAll() method");        // calling retainAll()        v1.retainAll(v2);          System.out.println("After calling retainAll() method");        System.out.println(v1);    }} |
Elements of vector1:[Geeks, For, Geeks, is, a, computer, science, portal]
Elements of vector2:[Geeks, For, Geeks, contains, well, written, programming, articles, and, much, more.]
Calling retainAll() method
After calling retainAll() method
[Geeks, For, Geeks]
Program 2:To show return value of retainAll() method in Java.
import java.util.*;import java.io.*;  public class GFG {    public static void main(String args[])    {          // Creating an empty Vector        Vector<String> v1 = new Vector<String>();          // adding elements to the vector v1        v1.add("Geeks");        v1.add("For");        v1.add("Geeks");        v1.add("is");        v1.add("a");        v1.add("computer");        v1.add("science");        v1.add("portal");          System.out.println("Elements of vector1:" + v1);          // Creating an other empty vector        Vector<String> v2 = new Vector<String>();          // adding elements to the vector v2        v2.add("Geeks");        v2.add("For");        v2.add("Geeks");        v2.add("contains");        v2.add("well");        v2.add("written");        v2.add("programming");        v2.add("articles");        v2.add("and");        v2.add("many");        v2.add("more.");          System.out.println("Elements of vector1:" + v1);          // calling retainAll()        boolean t = v1.retainAll(v2);          System.out.println("Calling retainAll() method: ");        System.out.println(t);    }} |
Elements of vector1:[Geeks, For, Geeks, is, a, computer, science, portal]
Elements of vector1:[Geeks, For, Geeks, is, a, computer, science, portal]
Calling retainAll() method:
true
