Beginner 20 min read

Numbers

By the end of this lesson, you'll be able to:

Choose the correct numeric type (Integer, Decimal, Long, Double) for a given value
Perform basic arithmetic with numeric variables
Explain why Decimal is generally preferred over Double for money

Prerequisites: "What Is a Variable?"

The four numeric types

Type	Holds	Typical use
`Integer`	Whole numbers, up to about 2.1 billion	Counts, ages, quantities
`Long`	Whole numbers, much larger than Integer	Very large IDs or counts
`Decimal`	Fixed-precision fractional numbers	Money, always
`Double`	Floating-point fractional numbers	Scientific/approximate values

A real business example: Banking

Decimal accountBalance = 1042.55;
Integer numberOfTransactions = 12;

Decimal accountBalance = 1042.55; — declares accountBalance as a Decimal (fixed-precision, exact fractional number) and sets it to 1042.55.
Integer numberOfTransactions = 12; — declares a whole-number count as an Integer.

accountBalance is a Decimal, never a Double — banking math needs exact precision, and Double can introduce tiny rounding errors from how computers represent fractional numbers internally. numberOfTransactions is a whole count, so Integer fits naturally.

Common mistakes

Using Double for money. This is the single most common numeric mistake in Apex — Double rounding errors can silently produce financial figures that are off by fractions of a cent, which compounds into real, confusing bugs.
Assuming Integer division gives a fractional result. 7 / 2 using two Integers gives 3, not 3.5 — division truncates unless at least one operand is a Decimal or Double.

Integer division truncates

Integer result = 7 / 2;
System.debug(result);          // 3, not 3.5

Decimal preciseResult = 7.0 / 2;
System.debug(preciseResult);   // 3.5

Integer result = 7 / 2; — divides two Integers. Apex performs integer division here, discarding any remainder, so result becomes 3, not 3.5.
System.debug(result); — logs result, confirming it printed 3.
(blank line)
Decimal preciseResult = 7.0 / 2; — writing 7.0 instead of 7 makes one operand a Decimal, so this time Apex performs fractional division.
System.debug(preciseResult); — logs preciseResult, which prints 3.5.

Exercise

Declare a Decimal called pricePerUnit (12.50) and an Integer called quantity (4). Calculate and debug the total cost.

Show hint

Decimal * Integer works fine in Apex — the result comes out as a Decimal.

Salesforce: ○ Not connected Connect

APEX

Execution Results

Run your code to see the result.

Numbers Quiz

1. Which numeric type should you use for money?

Decimal Double Long It does not matter

2. Dividing two Integers in Apex always produces a whole number result (the remainder is discarded).

True False

Leaderboard

1. Monde Masiza 2/2

My Notes

Questions about this lesson

No questions yet — be the first to ask.

Summary

Apex has four numeric types — Integer for whole numbers, Decimal for precise fractional values (like money), Long for very large whole numbers, and Double for less-precise fractional values — and picking the right one matters more than it might first appear.

❬ Previous Next ❭