To create a read-only list, use the unmodifiableList() method of the Collections class : ArrayList « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. ArrayList

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class MainClass {
  public static void main(String args[]) throws Exception {

    List list = new ArrayList();
    list.add("A");
    list.add("B");
    list.add("C");
    list = Collections.unmodifiableList(list);
    list.add(1, "G");

    System.out.println(list);

  }
}

Exception in thread "main" java.lang.UnsupportedOperationException
  at java.util.Collections$UnmodifiableList.add(Collections.java:1160)
  at MainClass.main(MainClass.java:14)