Beginner 10 min read

What Is an Expression?

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

Define "expression" and distinguish it from a statement
Identify expressions inside a line of Apex code
Explain that every expression evaluates to a single value

Prerequisites: Module 3: "Programming Basics: Variables & Data"

Expressions vs. statements

Integer total = 4 + 3;

Integer total = 4 + 3; — the part 4 + 3 is an expression: it evaluates to a single value, 7. The whole line is a statement — a complete instruction that does something (here, declares a variable and stores the expression's result in it).

Every expression, however complicated, boils down to one value once Apex finishes evaluating it.

Expressions can nest inside each other

Integer result = (4 + 3) * 2;

Integer result = (4 + 3) * 2; — 4 + 3 is an expression. (4 + 3) * 2 is a bigger expression, built out of the first one.

This is exactly how the rest of this module works: small operators combine into bigger, more useful expressions.

Common mistakes

Thinking a variable name alone isn\'t an expression. It is — total by itself evaluates to whatever value it currently holds, which is why System.debug(total); works at all.

Exercise

Write down three different expressions that would each evaluate to the number 10 (for example, 5 + 5). Try to make them structurally different from each other.

Show hint

Addition, multiplication, and subtraction can all reach 10 in different ways: 5+5, 2*5, 20-10.

What Is an Expression? Quiz

1. What does every expression eventually do?

Evaluate to exactly one value Print to the debug log Declare a new variable Always return a Boolean

Leaderboard

1. Monde Masiza 1/1

My Notes

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Summary

An expression is any piece of code that evaluates down to a single value — a number, a piece of text, true or false. Every operator you'll meet in this module exists to combine expressions into bigger ones.

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