[atp@gateway ~]$ cat aaa.java
import java.util.Vector;

public class aaa
{
　　public static void main (String [] s)
　　{
　　　　Vector<String> a = new Vector<String>();
　　　　a.add("hi");
　　　　Vector<String> b = (Vector<String>)a.clone();
　　　　System.out.println(b);
　　}
}
[atp@gateway ~]$ javac aaa.java
Note: aaa.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
[atp@gateway ~]$ java aaa
[hi]
[atp@gateway ~]$