Question

Give an example of a program that uses the nongeneric version of a class from the STL and the equivalent program that uses the generic version. How do the two implementations differ? Why is having the syntax of generics better?

Answer 1

Source Code in Java:

import java.util.ArrayList;
class NonGeneric
{
public static void main(String[] args)
{
ArrayList a=new ArrayList(); //creating object of ArrayList
//adding two elements to the ArrayList
a.add("Debjit");
a.add("Ganguli");
//calling get() to get the elements
String s1=(String)a.get(0);
String s2=(String)a.get(1);
//printing the elements
System.out.println(s1+" "+s2);
}
}

import java.util.ArrayList;
class Generic
{
public static void main(String[] args)
{
ArrayList<String> a=new ArrayList<String>(); //creating object of ArrayList for String elements
//adding two elements to the ArrayList
a.add("Debjit");
a.add("Ganguli");
//calling get() to get the elements
String s1=a.get(0);
String s2=a.get(1);
//printing the elements
System.out.println(s1+" "+s2);
}
}

Output:

The two implementations differ in that Generic class requires a type to be called, whereas Non-generic class does not.

The advantages of Generic classes are:

• Generic classes need to be written once for all data types, but Non-generic classes have to be written separately for every data type.
• Generic classes produce errors at compile time for type mismatch, but Non-generic classes generate errors at runtime for type mismatch.