Understanding Primitive Types and Wrapper Classes in Java: A Comprehensive Guide

In today’s blog post, we will be looking at a topic that every programmer goes trough in their early career as a software engineer or developer.

Why 🤷‍♂️? Because if you even do a tiny bit of coding each day, you most probably are using primitive types or wrapper classes.

I personally remember going trough primitive and wrapper classes in one of my first lessons about CS in university and the Udemy course I took.

Over the past few days, I found myself utilizing them extensively, prompting me to refresh my understanding of these concepts and, more specifically, why we prefer one over the other. I will be addressing this aspect in detail within this blog post!

What are we going to go over here:

• Primitive Types
• Wrapper Classes
• Why & When To Prefer One Over The Other
• BONUS: Autoboxing and Unboxing

🚨 Note! In this article, we will explore Java’s primitive types and wrapper classes. Although their use cases are quite similar across programming languages, we’ll focus on their specific applications in Java.

Primitive Types

These are the basic data types in Java that hold simple values. In Java, they are eight:

• boolean: boolean value, which is either true or false. Commonly used for logical operations and conditional statements.
• byte: 8-bit integer, ranging from -128 to 127. Bytes are often used when working with raw binary data or in scenarios where memory usage is critical.
• short: Shorts are useful when you need a larger range than bytes but don’t require the full range of an int, as it is a 16-bit integer, ranging from -32,768 to 32,767.
• int: The int type is a 32-bit integer, ranging from -2,147,483,648 to 2,147,483,647. Integers are the most commonly used numeric type in Java for general-purpose arithmetic operations.
• long: 62-bit integer, used when you need a larger range than ints, such as when dealing with very large numbers or timestamps.
• float: 32-bit value that can represent both integer and fractional numbers. Floating-point types are commonly used in scientific calculations or situations where decimal precision is required.
• double: a double-precision data type with 64-bit value, providing higher precision than float. Doubles are the default choice for representing decimal values in Java and are widely used in various mathematical calculations.
• char: represents any Unicode character, including those that occupy more than two bytes, and it is a 16-bit (2 bytes of memory) unsigned integer

Wrapper Classes

Not gonna dive much into the different wrapper classes we have in Java, as they are basically the primitive type, but wrapped in the form of an object. This provides additional functionalities, which shouldn’t be taken for granted.

👇 Here are all Wrapper classes and their related primitive type, as well as a code snippet, showcasing how to define each primitive type and transform it into a wrapper class object:

• Boolean: boolean

boolean primitiveBool = true;
Boolean wrapperBool = Boolean.valueOf(primitiveBool);

• Byte: byte

byte primitiveByte = 10;
Byte wrapperByte = Byte.valueOf(primitiveByte);

• Short: short

short primitiveShort = 100;
Short wrapperShort = Short.valueOf(primitiveShort);

• Integer: int

int primitiveInt = 1000;
Integer wrapperInt = Integer.valueOf(primitiveInt);

• Long: long

long primitiveLong = 100000L;
Long wrapperLong = Long.valueOf(primitiveLong);

• Float: float

float primitiveFloat = 3.14f;
Float wrapperFloat = Float.valueOf(primitiveFloat);

• Double: double

double primitiveDouble = 3.14159;
Double wrapperDouble = Double.valueOf(primitiveDouble);

• Character: char

char primitiveChar = 'A';
Character wrapperChar = Character.valueOf(primitiveChar);

In each case, the valueOf() method of the respective wrapper class is used to create an instance of the wrapper class from the corresponding primitive value. After the transformation, you can leverage all functionalities that wrapper classes come with!

Why & When To Prefer One Over The Other

The choice between using primitive types or wrapper classes in Java depends on several factors. Here are some considerations to help with the decision👇

Primitive Types

1. Simplicity and Efficiency: Primitive types are simple and more efficient in terms of memory usage and performance. They directly hold the value without any additional overhead of objects.
2. Memory and Performance Optimization: If you are working with a large number of values or performance-critical scenarios, using primitive types can be more efficient.
3. Working with Arrays: Primitive types can be used directly in arrays, which can be beneficial in scenarios where you need to store a large number of values in a compact manner.
4. Default Values: Primitive types have default values (e.g., 0 for numeric types, false for boolean), which can be useful in certain situations.

Wrapper Classes

1. Additional Functionality: Wrapper classes provide additional functionalities and utility methods that are not available in primitive types. For example, parsing, conversion, comparison, and utility methods for working with data.
2. Object-Oriented Features: Wrapper classes are objects, allowing them to be used in object-oriented programming paradigms, such as collections, generics, and polymorphism. Java’s collections and generics typically work with objects, not primitive types. Therefore, if you need to use primitive types in collections or generic classes, you would need to use the corresponding wrapper classes. For example, List<Integer> instead of List<int>.
3. Nullability: Wrapper classes can handle null values, whereas primitive types cannot. This can be useful when you need to represent the absence of a value or handle nullable variables.
4. API Requirements: Some APIs and libraries may specifically require the use of wrapper classes, especially when dealing with generic types or working with certain frameworks.

🎬 There are general use-cases for both primitive types and wrapper classes, but ultimately the choice depends on the specific needs and design considerations of your program.

BONUS: Autoboxing and Unboxing

Introduced in Java 5.0, autoboxing and unboxing are features:

✅ that allow for automatic conversion between primitive types and their corresponding wrapper classes. Autobox automatically converts primitive types to wrapper classes & the unboxing does the vice-verse!

✅ automatically recognized and done by the Java compiler.

Here is an example of how these Java features would play out in a real world case:

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

public class AutoboxingUnboxingExample {
    public static void main(String[] args) {
        List<Double> walletBalances = new ArrayList<>();

        // Autoboxing: Adding primitive integers to the list
        walletBalances.add(100.0);
        walletBalances.add(666.66);
        walletBalances.add(6969.0);

        // Unboxing: Retrieving primitive integers from the list
        int firstWallet = numbers.get(0);
        int secondWallet = numbers.get(1);
        int thirdWallet = numbers.get(2);

        System.out.println("First Wallet Balance: " + firstNumber);
        System.out.println("Second Wallet Balance: " + secondNumber);
        System.out.println("Third Wallet Balance: " + thirdNumber);
    }
}

In this example, we have a list called walletBalances of type Double (wrapper class for double). We can directly add primitive integers to the list without explicitly converting them into Double objects. This is an example of autoboxing.

Later, we retrieve the elements from the list using the get() method, and the elements are automatically unboxed into their corresponding primitive double values.

With these features and their PROS come a lot of dangers and CONS. Without going into much detail, here are some of the dangers we may face:

Performance & Memory overhead

Performance is impacted negatively by the generation of intermediate objects, which in turn increases the workload on the Garbage Collector.

Memory overhead is achieved, because wrapper objects consume more memory than primitive types, and creating unnecessary wrapper objects can result in increased memory overhead .. and this can be done very seamlessly when working with loops 👀

Readability

Overusing autoboxing and unboxing can make the code less readable and clear.

Implicit Conversions

If the expected types are not properly handled, the compiler may perform implicit conversions that differ from what was intended, potentially causing logic errors.

For example, in the following code snippet, the variable x is unboxed when compared with 0. This is something, we as engineers should take into account and keep in mind when developing!

Integer x = new Integer(5);
if (x > 0) {
  System.out.println("The number is greater than 0.");
}

📚 We’ve glanced over each primitive type and it’s related wrapper class, as well as the implications and the reasons as to why and when should we prefer one over the other, and to top it all off, we looked into the autobox & unbox features of Java.

🎊 With all that said, it’s safe to say that we’ve covered what’s to be known about the topic of primitive types & wrapper classes!

👋 I hope that you have gained new knowledge or had the opportunity to revisit these fundamental concepts of computer science!