9 Important differences between Integer and Int in Java


When diving into the world of Java programming, you often encounter various data types, each with its unique characteristics and uses. A common question that arises among beginners and even some experienced developers is: "What is the difference between integer and int in Java?"

In Java, int and Integer are used to store numeric values, specifically integers. However, they are not quite the same. int is a primitive data type, a fundamental piece of Java's data typing system, while Integer is a wrapper class that embodies the int primitive data type in an object.

In this tutorial, we will unravel the distinctions between int and Integer, touching on aspects such as memory consumption, performance, null handling, arithmetic operations, and many more enlightening topics. Our aim is to offer clarity, aiding you in making informed decisions on when to use which type based on your specific coding needs.

Stay with us as we explore the various dimensions in which int and Integer operate within the Java programming language, ensuring you grasp the essence of their differences and functionalities.


Basic Difference between Integer and Int in Java

Let's understand the very basic difference between integer and int in Java:

  • int as a Primitive: int is a primitive data type in Java. It’s a basic data type that is used to store integers without any additional methods or attributes. Being a primitive, int is more performance-efficient, and it’s utilized directly for mathematical operations.
  • Integer as an Object: On the contrary, Integer is an object. It is a part of the java.lang package and is a wrapper class for the int primitive data type. An Integer object stores a single int value, but it also has various methods and attributes, making it more versatile but slightly less performance-efficient compared to int.

Here are some examples:

Using int

int number = 100;
System.out.println(number); // Output: 100

Using Integer

Integer number = new Integer(100);
System.out.println(number); // Output: 100

Alternatively, you can use:

Integer number = 100; // Auto-boxing will occur here
System.out.println(number); // Output: 100

This table summarizes the main differences and considerations for using int and Integer in Java, helping you make more informed choices based on your specific programming needs.

Feature int (Primitive Type) Integer (Wrapper Class)
Basic Nature Primitive data type Object
Nullability Cannot be null Can be null
Memory Consumption Lower Higher due to object overhead
Performance Generally higher Slightly lower due to object overhead
Usage in Collections Not directly usable Directly usable
Serialization Not directly serializable Directly serializable
API Methods Availability Limited Rich API available
Arithmetic Operations Direct operations Unboxing may be necessary
Usage in Streams and Lambdas Requires specialized streams Directly usable
Type Conversion and Casting Manual casting required Auto-boxing/unboxing available
Best Practices Use for performance-critical parts Use where objects are required or nullability is necessary


Let's Explore Differences between Java Int and Integer

1. Memory Consumption

1.1 Memory Allocation for int

The int data type, being a primitive, is quite straightforward in terms of memory allocation. An int in Java typically consumes 4 bytes of memory. Here’s a simple illustration:

int number = 50;
// This will allocate 4 bytes of memory to store the integer value 50.

Explaining further, since an int is a primitive data type, it directly stores the value, making the memory usage constant and predictable.

1.2 Memory Allocation for Integer

Contrarily, the Integer class, as an object, consumes more memory. Apart from the 4 bytes used to store the actual integer value, additional bytes are used to support the object's metadata, such as method pointers. Here’s an example:

Integer number = new Integer(50);
// This allocates more memory compared to int due to object overhead.

Auto-boxing also plays a role in memory consumption:

Integer number = 50; // Auto-boxing
// This still has the overhead of object metadata, consuming more memory than a plain int.


2. Performance

2.1 Performance Implications of Using int

The int type, being a primitive, offers superior performance due to its straightforward nature. Operations with int values are executed directly, resulting in faster execution times. Here is a simple example:

int a = 5;
int b = 10;
int sum = a + b; // Direct and fast arithmetic operation

In this scenario, arithmetic operations like addition are performed swiftly due to the absence of object overhead, showcasing the practical performance difference between integer and int in Java.

2.2 Performance Implications of Using Integer

Integer, as an object, brings along additional overhead due to its object nature, leading to somewhat slower performance compared to int. Let's consider an example:

Integer a = 5; // Auto-boxing
Integer b = 10;
Integer sum = a + b; // Unboxing before the operation, then boxing again

Here, the unboxing of Integer objects to int values, performing the arithmetic operation, and then boxing the result back into an Integer object, takes additional processing time.


3. Null Handling

Handling null values is a significant difference between Integer and int in Java, affecting their usage and versatility.

3.1 How int Handles Null

Since int is a primitive data type, it cannot hold a null value. Attempting to assign a null value to an int variable results in a compilation error. Here is an illustrative example:

// int number = null; // This will cause a compilation error

3.2 How Integer Handles Null

Contrastingly, Integer being an object, can hold a null value, making it more flexible in scenarios where a null value might be a valid state. Here’s how it can be done:

Integer number = null; // Valid assignment


4. Arithmetic Operations

Arithmetic operations are fundamental in programming, and the choice between using int and Integer in Java can influence the ease and efficiency with which these operations are performed. Let’s explore the difference between Integer and int in Java in this context.

4.1 Performing Arithmetic Operations with int

Working with the int data type for arithmetic operations is straightforward due to its primitive nature. Operations like addition, subtraction, multiplication, and division are performed directly and efficiently. Here is a basic example:

int a = 5;
int b = 2;
int result = a + b; // Addition
System.out.println("Result: " + result); // Output: 7

The operations are executed swiftly and without any additional overhead, showcasing the benefits of using int for arithmetic processes.

4.2 Performing Arithmetic Operations with Integer

When it comes to Integer, arithmetic operations involve additional steps due to auto-boxing and unboxing. This implies that the Integer objects are converted to int values for the operation and then converted back. Here’s an illustrative example:

Integer a = 5;
Integer b = 2;
Integer result = a + b; // Unboxing, operation, and auto-boxing occur here
System.out.println("Result: " + result); // Output: 7

In this case, the operation involves implicit conversions (unboxing and auto-boxing), making arithmetic operations with Integer objects slightly less efficient compared to those with int.


5. Type Conversion and Casting

Type conversion and casting between int and Integer are common practices due to their interconnected nature. Let’s explore the automatic and manual methods of conversion to understand the difference between Integer and int in Java more profoundly.

5.1 Automatic Unboxing and Boxing

  • Boxing: Automatic conversion of primitive int to an object of Integer.
  • Unboxing: Automatic conversion of an Integer object to primitive int.

Here’s an example illustrating automatic boxing and unboxing:

int primitiveInt = 5;

// Automatic Boxing
Integer boxedInteger = primitiveInt; // The int is automatically boxed to an Integer object

// Automatic Unboxing
int unboxedInt = boxedInteger; // The Integer object is automatically unboxed to int

In this example, Java automatically handles the conversion, making the process seamless, thus highlighting a key aspect of the difference between integer and int in Java.

5.2 Manual Type Conversion Methods

Manual conversion involves explicitly converting data types using various methods available in the Integer class, such as valueOf() and intValue().

Manual Boxing Using valueOf():

int primitiveInt = 10;
Integer boxedInteger = Integer.valueOf(primitiveInt); // Manually boxing int to Integer

Manual Unboxing Using intValue():

Integer integerObject = new Integer(10);
int unboxedInt = integerObject.intValue(); // Manually unboxing Integer to int

In this example, manual methods are used for conversion, giving programmers more control over the process, but at the cost of verbosity.


6. Usage in Collections and Generics

Collections are a fundamental part of Java, allowing the grouping of multiple items. When it comes to using int and Integer within collections, their applicability varies, showcasing a significant difference between Integer and int in Java.

6.1 Using int in Collections

Direct usage of int in collections such as ArrayList or HashMap is not possible because collections only store objects, and int is a primitive data type. However, auto-boxing allows implicit conversion of int to Integer, enabling its use in collections indirectly.

List<int> numbers = new ArrayList<int>(); // This is not valid

List<Integer> numbers = new ArrayList<>();
numbers.add(5); // The int value is auto-boxed to Integer

In this scenario, despite using an int value, Java automatically converts it to Integer, allowing it to be stored in the collection.

6.2 Using Integer in Collections

Integer, being an object, is naturally suited for use within collections. Its direct applicability makes it a more convenient choice in such contexts.

List<Integer> numbers = new ArrayList<>();
numbers.add(new Integer(5)); // Directly adding an Integer object

// or

Integer number = 5;
numbers.add(number); // Adding an existing Integer object

Here, Integer objects are directly added to the collection, showcasing their compatibility and ease of use in such data structures.


7. Usage in Streams and Lambdas

Java’s Streams API and lambda expressions offer powerful tools for processing collections and other data structures. The utilization of int and Integer within streams and lambdas further accentuates the difference between Integer and int in Java.

7.1 int Usage in Streams and Lambdas

Streams and lambdas primarily operate on objects. However, the usage of int is facilitated through specialized streams such as IntStream. This allows for efficient operations on primitive values, as demonstrated below:

IntStream intStream = IntStream.of(1, 2, 3, 4, 5);
int sum = intStream.sum(); // Directly using int values in a stream
System.out.println("Sum: " + sum);

In this example, an IntStream is utilized to perform operations directly on int values, showcasing its tailored support for primitive types.

7.2 Integer Usage in Streams and Lambdas

Integer objects naturally integrate with streams and lambdas due to their object nature, as illustrated below:

List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
int sum = integers.stream()
System.out.println("Sum: " + sum);

Here, a list of Integer objects is processed using a stream and a lambda expression, demonstrating the ease with which Integer objects interact with these advanced Java features.


8. Serialization

Serialization is the process of converting an object into a byte stream, enabling it to be saved or transmitted and then reconstructed. The approach to serialization varies when dealing with int and Integer, underscoring another crucial difference between Integer and int in Java.

8.1 Serializing int

Since int is a primitive data type, it doesn’t implement the Serializable interface directly. However, int values can be serialized when they are part of a serializable object. Here’s an example:

import java.io.*;

class Data implements Serializable {
    int number;

    public Data(int number) {
        this.number = number;

// Serialization process
try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("data.ser"))) {
    Data data = new Data(5);
} catch (IOException e) {

In this example, the int value is serialized as part of a serializable object, demonstrating how it can be involved in the serialization process indirectly.

8.2 Serializing Integer

Integer objects, being instances of a class, are inherently serializable as the Integer class implements the Serializable interface. This makes the serialization process more straightforward:

import java.io.*;

// Serialization process
try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("integer.ser"))) {
    Integer number = 5;
} catch (IOException e) {

In this case, the Integer object is directly serialized, reflecting the inherent compatibility of Integer with the serialization mechanisms in Java.


9. API Methods

Java’s API provides a variety of methods that facilitate operations on numbers. The availability of these methods varies between Integer and int, showcasing a notable difference between Integer and int in Java.

9.1 Common Integer Class Methods

The Integer class comes enriched with a multitude of methods that allow for a diverse range of operations such as parsing, comparing, and converting integers. Here’s a demonstration of some common methods:

// Parsing an Integer
String numberString = "123";
Integer number = Integer.parseInt(numberString); // Converts string to Integer
System.out.println(number); // Output: 123

// Converting Integer to Binary
String binaryString = Integer.toBinaryString(number); 
System.out.println(binaryString); // Output: 1111011

These examples illustrate the utility of Integer class methods in performing various operations, emphasizing the versatility of Integer objects.

9.2 Lack of Associated Methods with int

Contrastingly, int being a primitive data type, doesn’t have associated methods. Operations on int values are usually direct and don’t require method invocations:

int number = 123;

// Arithmetic operation
int result = number * 2; // Direct multiplication
System.out.println(result); // Output: 246

Despite this, int values can be used as arguments in Integer class methods, which act as utility methods for int:

// Converting int to Hexadecimal
String hexString = Integer.toHexString(number);
System.out.println(hexString); // Output: 7b


Best Practices

When choosing between int and Integer in Java, applying best practices based on the specific needs of a task or application is essential. This choice can influence various aspects such as performance, null handling, and API access, underlining the difference between Integer and int in Java.


When to Use int

Performance-Sensitive Contexts: Since int is a primitive data type, operations on int values tend to be faster and more efficient.

int result = 0;
for(int i = 0; i < 1000; i++) {
    result += i; // Direct arithmetic operations on primitive types are efficient

Simple Arithmetic Operations: For scenarios where the main task involves basic arithmetic without necessitating object methods or null handling, int is a suitable choice.

int a = 5;
int b = 10;
int sum = a + b; // Simple and efficient


When to Use Integer

In Collections and Generics: Integer should be preferred when working with collections, as they require object types.

List<Integer> numbers = new ArrayList<>();
numbers.add(1); // Storing integers as objects in collections

When Null Handling is Necessary: Integer allows for the representation of null, making it suitable in cases where null values need to be accommodated and handled.

Integer value = null; // Integer can hold null, providing flexibility in handling absence of value

API Method Access: Utilizing Integer provides access to a wide array of utility methods in the Integer class, which can be advantageous for various operations and conversions.

Integer number = 5;
String hex = Integer.toHexString(number); // Access to a variety of utility methods


Frequently Asked Questions

What is the main difference between int and Integer in Java?

The primary difference lies in their nature; int is a primitive data type, while Integer is a class, making it an object. This object, known as a wrapper, allows for methods and operations that aren’t directly applicable to int. Integer can be used in a wider array of contexts, such as in collections and where null values are permissible.

Can int and Integer be used interchangeably in Java?

Java provides auto-boxing and unboxing features, enabling a degree of interchangeability. However, fundamental differences such as handling null values, method availability, and usage in generic data types make them distinct in various contexts.

Is there a performance difference between int and Integer?

Yes, int is more performance-efficient. It’s a primitive data type and directly holds values, resulting in faster operations and lesser memory consumption compared to the Integer object, which comes with additional overhead.

Can int be null in Java?

No, int can’t be null as it’s a primitive data type that directly holds numerical values. Integer, being an object, can hold a null value, indicating the absence of a value.

Where should int and Integer be used in terms of collections?

Collections in Java store objects, making Integer more suitable for use in collections like ArrayList and HashMap. int, being a primitive, isn’t directly usable in generic collections.

How does serialization handle int and Integer?

Integer is inherently serializable, simplifying the serialization process. On the contrary, int needs to be part of a serializable object to be serialized, as it’s not an object itself.

What kind of arithmetic operations can be performed on int and Integer?

Both types support basic arithmetic operations. int performs these with better efficiency due to its primitive nature, while Integer has access to a variety of utility methods that offer added functionality beyond basic arithmetic.

Can int and Integer values be used directly in streams and lambdas?

While Integer can be used directly, int requires specialized streams like IntStream for effective use in lambda expressions and stream operations, promoting efficiency and type-safety.

How do int and Integer handle type conversion and casting?

Integer encompasses methods for conversions, like toString. int requires explicit casting for conversions. Automatic conversions occur due to auto-boxing and unboxing, smoothing the interchange between int and Integer.

Which is more memory-efficient, int or Integer?

int` proves more memory-efficient, as it represents values directly, avoiding the additional overhead present in `Integer` objects due to object metadata and methods.



In the exploration of the difference between Integer and int in Java, we've traversed through various facets that distinguish these two types, ranging from their basic nature, memory consumption, to their usability in different contexts like collections and streams.

Summarizing Key Takeaways

  • Basic Nature: int is a primitive data type, while Integer is an object, a wrapper class in Java.
  • Memory and Performance: int is more performance-efficient compared to Integer due to less memory consumption and direct value access.
  • Null Handling: Integer can handle null values, whereas int cannot.
  • Usage in Collections: Integer is inherently usable in collections and generics, thanks to its object nature, unlike int.
  • API Methods and Operations: Integer comes with a suite of utility methods, while int operations are mainly straightforward arithmetic.

Further Reading Resources:


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Deepak Prasad

Deepak Prasad

He is the founder of GoLinuxCloud and brings over a decade of expertise in Linux, Python, Go, Laravel, DevOps, Kubernetes, Git, Shell scripting, OpenShift, AWS, Networking, and Security. With extensive experience, he excels in various domains, from development to DevOps, Networking, and Security, ensuring robust and efficient solutions for diverse projects. You can connect with him on his LinkedIn profile.

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