Vector Immutability : Vector « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. Vector

import java.util.Collections;
import java.util.List;
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);
    System.out.println(v.size());

    List l = Collections.unmodifiableList(v);

    l.add(1);
    System.out.println(l);
  }
}

[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
Exception in thread "main" java.lang.UnsupportedOperationException
	at java.util.Collections$UnmodifiableCollection.add(Collections.java:1018)
	at MainClass.main(MainClass.java:16)