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Unit 3: Boolean Expressions and if Statements

7 dot points across 7 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do relational operators build boolean expressions, and what value does each one produce?

Topic 3.1 Boolean Expressions: evaluate expressions formed with the relational operators (<, >, <=, >=, ==, !=) that produce a boolean result of true or false.
A focused answer to AP CSA Topic 3.1, covering the six relational operators, how they compare numeric primitives to produce a boolean, the difference between == and =, comparing doubles, and how relational operators combine with arithmetic, with a fully traced worked evaluation.
10 min answer →

How do you compare objects in Java, and why does == differ from the equals method?

Topic 3.7 Comparing Objects: compare object references with == and !=, compare object contents with equals, and detect a null reference, understanding the difference between identity and equality.
A focused answer to AP CSA Topic 3.7, covering reference equality with == and !=, content equality with the equals method, comparing against null, why two equal-looking objects can be unequal by ==, and using equals/compareTo for Strings, with a fully worked example.
10 min answer →

How do the logical operators &&, || and ! combine conditions, and what is short-circuit evaluation?

Topic 3.5 Compound Boolean Expressions: combine boolean expressions with the logical operators && (and), || (or) and ! (not), applying short-circuit evaluation.
A focused answer to AP CSA Topic 3.5, covering the logical operators && , || and !, their truth tables, operator precedence and short-circuit evaluation, why short-circuiting prevents errors, and how to trace a compound condition, with a fully worked example.
11 min answer →

How does an else if chain select one outcome from several mutually exclusive options?

Topic 3.4 else if Statements: use an if / else if / else chain so that the first true condition runs its block and the rest are skipped, selecting exactly one outcome.
A focused answer to AP CSA Topic 3.4, covering the if / else if / else chain, why the first true condition wins and later ones are skipped, why ordering matters, the role of the final else, and how to trace a multi-branch decision, with a fully worked example.
10 min answer →

How do De Morgan's laws let you rewrite a negated boolean expression into an equivalent one?

Topic 3.6 Equivalent Boolean Expressions: apply De Morgan's laws and truth tables to produce equivalent boolean expressions and to simplify negations of compound conditions.
A focused answer to AP CSA Topic 3.6, covering De Morgan's laws for negating && and ||, using truth tables to prove equivalence, simplifying double negation, and rewriting conditions to remove a leading !, with a fully worked example.
10 min answer →

How does an if-else statement choose between two alternative blocks of code?

Topic 3.3 if-else Statements: use a two-way if-else statement so that exactly one of two code blocks runs depending on whether the boolean condition is true or false.
A focused answer to AP CSA Topic 3.3, covering two-way selection with if-else, the guarantee that exactly one branch runs, how the else attaches to the nearest if, nested if-else, and how to trace each branch, with a fully worked example.
10 min answer →

How does an if statement use a boolean condition to control which statements run?

Topic 3.2 if Statements and Control Flow: use a one-way if statement so that a block of code runs only when its boolean condition is true, and trace the resulting flow of control.
A focused answer to AP CSA Topic 3.2, covering the syntax of a one-way if statement, the role of the boolean condition, why braces matter, the dangling-statement trap, and how control flows through and past the if, with a fully traced worked example.
10 min answer →