2.2 If Statements and Control Flow

Basic if statement

An if statement lets a program execute code only when a boolean expression evaluates to true. Syntax: `if (condition) { statement(s); }`. If the condition is false, the block is skipped entirely and control flow moves to the code after the if statement.

if-else and control flow

An if-else statement provides an alternative path: if the condition is true, the if-block runs; otherwise, the else-block runs. Only one branch ever executes. This creates a fork in the program's control flow, meaning statements execute conditionally instead of strictly top to bottom.

Nested and chained conditionals

You can nest if statements inside other if/else blocks to test multiple conditions, or chain them using else if to check several mutually exclusive options in order. Only the first true condition's block executes; the rest are skipped, even if they'd also be true.

Key terms

if statement

A control structure that executes a block of code only if its boolean condition is true.

if-else statement

Executes the if-block when the condition is true, otherwise executes the else-block; only one runs.

else if chain

A sequence of conditions checked in order; only the first true condition's block executes.

Nested if statement

An if statement placed inside another if or else block, used to test additional conditions.

Control flow

The order in which statements execute; conditionals like if/else create branching paths instead of strict top-to-bottom execution.

Try an AP-style question

int x = 10;
if (x > 5)
    x = x * 2;
x = x + 1;

What is x?

1. 20
2. 10
3. 11
4. 21