AP Computer Science A: Selection and Iteration

Selection

A control structure that allows a program to choose between multiple execution paths based on boolean conditions.

Iteration

A programming technique that repeatedly executes a block of code while a condition is true

if Statement

Executes a block of code when the given condition evaluates to true.

if-else Statement

Executes one block if the condition is true, and another block if it is false.

Nested if

An if statement placed inside another to handle multiple conditions

switch Statement

A multi-way selection structure that executes code based on the value of an expression, often used with int, enum, or String types.

Boolean Expression

An expression that evaluates to either true or false, often using relational or logical operators.

Relational Operators

Operators that compare two values: ==, !=, >, <, >=, <=.

Logical Operators

Operators used to combine boolean expressions: && (and), || (or), ! (not).

Short-Circuit Evaluation

The process where logical expressions stop evaluating as soon as the result is determined (e.g., in &&, if left side is false, right side isn’t evaluated).

De Morgan’s Laws

Rules for negating boolean expressions:

!(A && B) → !A || !B, and !(A || B) → !A && !B.

Equality vs. Assignment

== tests equality, while = assigns a value. Using = in a condition is a logic error

.equals() Method

Compares object contents, not references (used for Strings or other objects)

Ternary Operator

A compact conditional expression in the form (condition ? trueValue : falseValue).

while Loop

A loop that tests its condition before executing its body; executes zero or more times.

do-while Loop

Executes the loop body once before checking the condition; always runs at least once.

for Loop

A counting loop with an initialization, condition, and update in a single line.

Enhanced for Loop

A simplified loop for iterating over arrays or collections (read-only access).

Loop Control Variable

A variable that controls the number of loop iterations, typically incremented or updated each pass.

break Statement

Exits the nearest enclosing loop immediately.

continue Statement

Skips the rest of the current iteration and moves to the next loop cycle

Infinite Loop

A loop that never terminates because its condition always remains true.

Sentinel-Controlled Loop

A loop that continues until a special value (sentinel) is encountered, often used with user input.

Counter-Controlled Loop

A loop that repeats a known number of times using a loop counter variable.

Accumulator Pattern

A loop pattern used to compute totals or sums by repeatedly adding values to a variable.

Nested Loop

A loop inside another loop; used for multi-dimensional data but increases time complexity (O(n²)).

Loop Invariant

A statement that is true before and after each loop iteration, useful for reasoning about loop correctness

Off-by-One Error

A common mistake in loops caused by incorrect boundary conditions (e.g., using < instead of <=)

Time Complexity

A measure of how loop execution time grows with input size; single loop = O(n), nested loop = O(n²).