Retaining Another Collection: public boolean retainAll(Collection c) : Vector « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. Vector

Only those elements within the collection argument are kept within the vector. Everything else is removed instead.

import java.util.Vector;

public class MainClass {
  public static void main(String args[]) {
    Vector v = new Vector(5);
    for (int i = 0; i < 10; i++) {
      v.add(0,i);
    }
    System.out.println(v);
  
    Vector v2 = new Vector(5);
    for (int i = 0; i < 5; i++) {
      v2.add(0,i);
    }
    System.out.println(v2);
    System.out.println(v2.equals(v));
    
    v.retainAll(v2);
    System.out.println(v);
  }
}

[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
[4, 3, 2, 1, 0]
false
[4, 3, 2, 1, 0]