Statements

Statements - Boolean Expressions Boolean expression is just...

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1 Boolean Expressions • Boolean expression is just a test for a condition • Essentially, evaluates to true or false • Value comparisons: == “equals” (note: not single = ) != “not equals” (cannot say <> ) > “greater than” < “less than” >= “greater than or equal to” <= “less than or equal to” More Boolean Expressions • Boolean comparisons (in order of precedence): ! “not” !p if p is true, then !p is false, and vice versa && “and” p && q only true if p and q are both true || “or” p || q true if p or q (or both) are true boolean p = (x != 1) || (x != 2); p is always true , you really want: boolean p = (x != 1) && (x != 2); Short Circuit Evaluation Stop evaluating boolean expression as soon as we know the answer Consider: p = (5 > 3) || (4 <= 2); The test (4 <= 2) is not performed! Example of useful case: p = (x != 0) && ((y / x) == 0); Avoid division by 0, since ((y / x) == 0) is not performed Statement Blocks • A Compound statement (or block) is a set of statements enclosed in braces { int x = 5; double y = readDouble("y: "); println("y = " + y); } • Variable’s scope
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Statements - Boolean Expressions Boolean expression is just...

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