• Generics is used to make  the data type safe program. It is the new feature of java 5.
• When the ArrayList is generalized for a specific data type, other data types cannot be added.
• It gives error on using the other data type element.

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

public class GenericList1 {
    public static void main(String[] args) {
      List list=new ArrayList();
         list.add("aaa");
         list.add("bbb");
         list.add(1000);
         list.add("ccc");
         list.add("ddd");
         System.out.println(list);
    }
}
It gives compilation error
GenericList1.java:9: cannot find symbol
symbol : method add(int)
location: interface java.util.List
list.add(1000);
^
1 error
Example-2
import java.util.ArrayList;
import java.util.List;

public class GenericList2 {
    public static void main(String[] args) {
      List list=new ArrayList();
         list.add("aaa");
         list.add("bbb");
         list.add("fff");
         list.add("ccc");
         list.add("ddd");
         System.out.println(list);
    }
}
Output
[aaa, bbb, fff, ccc, ddd]

Related Tags for Java arraylist generics example and arraylist generic list: