Java Wrapper Class

In this tutorial, we will learn about the Java Wrapper class with the help of examples.

A Wrapper class is a class whose object wraps or contains primitive data types. When we create an object to a wrapper class, it contains a field and in this field, we can store primitive data types. In other words, we can wrap a primitive value into a wrapper class object.Wrapper classes provide a way to use primitive data types (int, boolean, etc..) as objects.

Example:

public class MyClass {
  public static void main(String[] args) {
    Integer myInt = 5;
    Double myDouble = 5.99;
    Character myChar = 'A';
    System.out.println(myInt);
    System.out.println(myDouble);
    System.out.println(myChar);
  }
}
Output:
5
5.99
A

Need of Wrapper Classes

• They convert primitive data types into objects. Objects are needed if we wish to modify the arguments passed into a method (because primitive types are passed by value).
• The classes in java.util package handles only objects and hence wrapper classes help in this case also.
• Data structures in the Collection framework, such as ArrayList and Vector, store only objects (reference types) and not primitive types.
• An object is needed to support synchronization in multithreading.

Autoboxing

Automatic conversion of primitive types to the object of their corresponding wrapper classes is known as autoboxing. For example – conversion of int to Integer, long to Long, double to Double etc.

Unboxing

It is just the reverse process of autoboxing. Automatically converting an object of a wrapper class to its corresponding primitive type is known as unboxing. For example – conversion of Integer to int, Long to long, Double to double, etc.