Why Generics

Example

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

public class Main {
    @SuppressWarnings({ "rawtypes", "unchecked" })
    public static void main(String[] args) {
        List raw = new ArrayList();          // raw type: no type checking
        raw.add("Asha");
        raw.add(42);                         // compiler does not complain
        for (Object o : raw) {
            try {
                String s = (String) o;
                System.out.println("Name: " + s);
            } catch (ClassCastException e) {
                System.out.println("Crash at runtime for value " + o);
            }
        }

        List<String> names = new ArrayList<>();   // generic: checked at compile time
        names.add("Ravi");
        // names.add(42);                    // compile error: incompatible types
        String first = names.get(0);         // no cast needed
        System.out.println("Generic list gives: " + first);
    }
}

Output

Name: Asha
Crash at runtime for value 42
Generic list gives: Ravi