BigInteger and BigDecimal

Learn precise calculations with big numbers.

What are BigInteger and BigDecimal?

For very large numbers or high-precision calculations, Java offers the BigInteger and BigDecimal classes. They live in the java.math package.

BigInteger holds integers of unlimited size; use it for values that exceed long.

BigDecimal holds decimals with high precision. It is used for money instead of double, because double can introduce rounding errors.

import java.math.BigDecimal;
BigDecimal price = BigDecimal.valueOf(19.99);

Exercise Add with BigDecimal

Write a Main class with a main method. Add import java.math.BigDecimal; at the top. Assign BigDecimal.valueOf(9.99) to BigDecimal price and BigDecimal.valueOf(2.50) to BigDecimal shipping. Print price.add(shipping) with println.

Show example solution

import java.math.BigDecimal;

public class Main {
    public static void main(String[] args) {
        BigDecimal price = BigDecimal.valueOf(9.99);
        BigDecimal shipping = BigDecimal.valueOf(2.50);
        System.out.println(price.add(shipping));
    }
}

When to use BigDecimal?

For money, interest and tax calculations, decimal precision is critical. Because of binary representation, double gives 0.1 + 0.2 as 0.30000000000000004, which causes wrong results for money.

BigDecimal uses decimal representation, so BigDecimal.valueOf(0.1).add(BigDecimal.valueOf(0.2)) gives exactly 0.3.

Instead of arithmetic operators, this class uses methods like add, subtract, multiply, divide. They are slower, but accuracy matters more.

Test yourself

Match the classes

BigInteger

Unlimited integer
BigDecimal

Precise decimal
long

64 bit
double

Binary decimal

Complete the BigDecimal value

BigDecimal pi = BigDecimal.valueOf(____);

Show answer

BigDecimal pi = BigDecimal.valueOf(3.14);

Which is best for money calculations?
- double
- BigDecimal
- float
- int
Show answer

BigDecimal — BigDecimal avoids rounding loss.

Next lesson: Summary - Data types

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies