Java int vs Integer

In this guide, you will learn the differences between int and Integer. Both of these are the data types that represents integer values. However they serve different purposes and usages.

int

• Primitive Data Type: int is a primitive data type in Java.
• Memory Efficiency: It takes less space in memory compared to Integer so it is more memory efficient. It takes 4 bytes compared to 16 bytes taken by Integer.
• Default Value: The default value of an int is 0.
• No Methods: int is a primitive data type, hence it doesn’t have any methods associated with it.
• Usage: Commonly used in arithmetic operations.

Integer

• Wrapper Class: Integer is a wrapper class that belongs to java.lang package.
• Object: Integer is a class so an object can be created for this class. It can be used where objects are required for example, collections (e.g., LinkedList<Integer>).
• Memory Overhead: Integer takes more space in memory compared to int because they store metadata along with actual data.
• Default Value: The default value of an Integer is null.
• Methods: Integer class provides several useful methods such as intValue(), parseInt(), toString(), valueOf() etc.
• Autoboxing and Unboxing: The autoboxing and unboxing feature of Java provides automatic conversion between int and Integer.

Java int vs Integer Example

Let’s take an example to understand the key differences between these two.

public class IntVsInteger {
    public static void main(String[] args) {
        // Using int
        int primitiveInt = 5;
        System.out.println("Primitive int: " + primitiveInt);

        // Using Integer
        Integer wrapperInt = 10;
        System.out.println("Wrapper Integer: " + wrapperInt);

        // Autoboxing: int to Integer Conversion
        Integer autoBoxedInt = primitiveInt;
        System.out.println("int to Integer: " + autoBoxedInt);

        // Unboxing: Integer to int Conversion
        int unboxedInt = wrapperInt;
        System.out.println("Integer to int: " + unboxedInt);

        // Demonstrating methods of Integer class
        String intString = Integer.toString(primitiveInt);
        int parsedInt = Integer.parseInt(intString);
        System.out.println("Parsed int from String: " + parsedInt);
    }
}

Key Differences

• Memory and Performance: int is more memory-efficient and faster compared to an Integer.
• Nullability: Integer can be null because it is an object, while int cannot be null, they have default 0 value.
• Collections: When working with Collections such as ArrayList, LinkedList, HashMap etc, Integer is preferred because these collections require objects.