Check code below
import java.util.*;
public class
Test {
public static void main (
String args []) {
List<Number>x=new ArrayList<Number>();
x.add(new Integer("10"));
take(x);
take1(x);
}
public static void take(List<? extends Number>x){
//In this method nothing can be added to List x
//This method becomes read only method
System.out.println(x.get(0));
}
public static void take1(List<? super Number>x){
//In this method anything extends Number can
//be added to List x
x.add(new Integer("20"));
x.add(new Long("20"));
x.add(new Float("20.120"));
for(Object n:x){
System.out.println(n);
}
}
}