java Compilation

import java .util.*; class ArrayListDemo { public static void main(String[] args) { ArrayList l=new ArrayList(); l.add("A"); l.add(10); l.add(null); System.out.println(l); l.remove(2); System.out.println(l); l.add(2,"M"); l.add("N"); System.out.println(l); } }

in the above java program compilation time following error is occur in my system

Note: ArrayListDemo.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 1 error

so plz send me answer why this error is coming............ and what is the reason and solution ....

July 30, 2012 at 10:19 AM

This comes up in Java 5 and later if you're using collections without type specifiers (e.g., Arraylist() instead of ArrayList<Object>()). It means that the compiler can't check that you're using the collection in a type-safe way, using generics.

To avoid this error, specify the type of object you're storing in the collection. So, specify the type as the following:

ArrayList<Object> l= new ArrayList<Object>();

In your code, you have added integer as well as string values to list therefore you need to use Object. Otherwise, whatever values you added, specify the type specifier.