Why do we need wrapper classes?

Wrapper classes are needed when primitive data types must be treated as objects. They provide additional functionality, support Java Collections and Generics, and offer utility methods for data conversion and manipulation.

Key Points: • Collections Framework classes such as ArrayList and HashMap can store only objects, not primitive types. • Wrapper classes provide useful utility methods such as parseInt(), valueOf(), compareTo(), and toString(). • They enable Autoboxing and Unboxing, allowing automatic conversion between primitives and objects. • Wrapper classes can represent null values, unlike primitive data types. • They are immutable and final, making them safe and reliable to use.

Example: An ArrayList cannot store int values directly, so Integer wrapper objects are used instead.

Code Example:

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

public class Demo {

    public static void main(String[] args) {

        List<Integer> numbers = new ArrayList<>();

numbers.add(10); // Autoboxing

int value = numbers.get(0); // Unboxing

        System.out.println(value);
    }
}

Interview Tip: A concise interview answer is:

"We need wrapper classes because many Java APIs, Collections, and Generics work only with objects. Wrapper classes also provide utility methods, support null values, and enable automatic conversion between primitive types and objects through autoboxing and unboxing."