Java Program to demonstrate Integer wrapper class

Program

import java.lang.Integer;
public class javaLangIntegerDemo
{
	public static void main (String[]args)
	{
		Integer iObj = new Integer(100);
		System.out.println ("Value of Integer object : " + iObj);
	}
}

Purpose

This Java program demonstrates the use of the Integer wrapper class to create an object that represents an integer value and how to use it.

1. Import Statement

import java.lang.Integer;

• The Integer class is part of the java.lang package, which is automatically imported in Java. The explicit import statement here is optional.
• Integer is a wrapper class that provides an object representation for primitive int values.

2. Class Definition

public class javaLangIntegerDemo

• Defines the class javaLangIntegerDemo.

3. Main Method

public static void main (String[] args)

• Entry point for the program.

4. Create an Integer Object

Integer iObj = new Integer(100);

• Integer Constructor:
  • Creates an object of the Integer wrapper class that stores the value 100.
  • This object is an instance of the Integer class, which wraps the primitive int value 100.
• Note:
  • The constructor new Integer(int value) is deprecated in modern Java versions. You should use Integer.valueOf(100) or simply 100 (autoboxing) instead.

5. Print the Value

System.out.println ("Value of Integer object : " + iObj);

• Prints the value stored in the Integer object.
• The toString() method of the Integer class is implicitly called to convert the object to a string for display.

Key Concepts

1. Wrapper Classes:

   • A wrapper class provides an object representation for primitive data types. In this case, Integer is the wrapper class for the primitive type int.

2. Why Use Wrapper Classes?

   • To treat primitive data types as objects.
   • Useful in collections like ArrayList, which only work with objects.
   • Provide utility methods for conversion, parsing, and handling numbers.

3. Autoboxing and Unboxing:

   • Autoboxing: Automatically converts a primitive type to its wrapper class. Example:

     Integer iObj = 100; // Autoboxing
     

   • Unboxing: Automatically converts a wrapper class object to its primitive type. Example:

     int primitiveValue = iObj; // Unboxing
     

Output

Value of Integer object : 100