What are the core concepts covered in Primitives, Wrapper Classes & BigDecimal?

8 Primitive types in Java and memory sizes; Autoboxing and unboxing between int and Integer; Why double/float must never be used for money (use BigDecimal)

Intermediate 14 min readModule: Module 2: Data Types, Variables & Operators

Primitives, Wrapper Classes & BigDecimal

Master Java primitive types, autoboxing, and avoid floating point rounding errors with BigDecimal.

What You Will Learn in This Lesson

8 Primitive types in Java and memory sizes
Autoboxing and unboxing between int and Integer
Why double/float must never be used for money (use BigDecimal)

Introduction & Core Concept

Java has 8 primitive data types (byte, short, int, long, float, double, boolean, char) stored directly on the stack for high speed.

WHY DOES THIS MATTER IN THE REAL WORLD?

Using double for monetary calculations produces rounding errors (0.1 + 0.2 = 0.30000000000000004). BigDecimal guarantees exact decimal precision.

Exact Financial Math with BigDecimal

java

1
2
3
4
5
6
7
8
9
10
import java.math.BigDecimal;
 
public class FinancialApp {
    public static void main(String[] args) {
        BigDecimal price = new BigDecimal("19.99");
        BigDecimal tax = new BigDecimal("0.08");
        BigDecimal total = price.add(price.multiply(tax));
        System.out.println("Exact Total: $" + total.setScale(2, BigDecimal.ROUND_HALF_UP));
    }
}

Line-by-Line Technical Breakdown

1Wrapper classes (Integer, Double) allow primitives to be used in generic collections like List<Integer>.

Try It Yourself (Interactive Editor)

Modify the code in real-time and click Run to test live browser output and console logs.

Intelligent Code Runner & Live Sandbox[JAVA]

JAVA SOURCE EDITOR

Interactive Live Code

>javac -parameters Main.java && java -XX:+UseZGC Main

>Exact Total: $" + total.setScale(2, BigDecimal.ROUND_HALF_UP)

Industry Best Practices & Professional Standards

Always instantiate BigDecimal using string constructors (new BigDecimal('19.99')).

Lesson Summary & Core Takeaways

Precise data types prevent subtle calculation bugs in financial software.