05_Conditionals_and_Loops

05_Conditionals_and_Loops - 5. Conditionals and Loops...

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COMP 1210 – Fundamentals of Computing I Slide 5 - 1 5. Conditionals and Loops • Objectives - when we have completed this chapter, you should be familiar with: flow of control: sequence, selection, iteration boolean expressions selection: if and if-else statements iteration: while loops equality, relational, and logical operators block statements comparing objects nested while loops Iterators the ArrayList class
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COMP 1210 – Fundamentals of Computing I Slide 5 - 2 Flow of Control Sequence - Unless specified otherwise, the order of statement execution through a method is sequential, one statement after another Selection - statements that allow us to decide whether or not to execute a particular statement (or block of statements); that is, select among alternatives Examples: if , if-else , switch statements Iteration (repetition) - statements that allow us to execute a statement (or block of statements) over and over, repetitively Examples: while , do-while , for statements (or loops) • Iteration and Selection statements (except switch ) use boolean expressions that evaluate to true or false to determine whether a statement (or block of statements) is executed • The order of statement execution in a method is called the flow of control
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COMP 1210 – Fundamentals of Computing I Slide 5 - 3 Flow of Control Flow of control : the order in which statements are executed in a program When we read source code, the sequence, selection, and iteration is relative to the method we’re reading Example: In the main method we may have 10 statements that are executed in sequence. If one of the statements invokes/calls a method and we step in (or jump) to that method, we will encounter sequence and possibly selection and/or iteration in this method You can use the debugger to follow the detailed flow of control (see examples in later slides) Q
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COMP 1210 – Fundamentals of Computing I Slide 5 - 4 Boolean Expressions • Boolean expression: an expression that evaluates to true or false. Example: (where num1 and num2 are int values) num1 > num2 + 5 • A boolean variable can be assigned the result of a boolean expression: Example: (where email references a String object) boolean validEmail = email.contains( "@" ); boolean expression
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COMP 1210 – Fundamentals of Computing I Slide 5 - 5 Boolean Expressions • An if statement uses a boolean expression as its condition: Example: temp is a double value representing outdoor temperature if (temp > 80) { System.out.println( "Stay indoors." ); } boolean expression
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COMP 1210 – Fundamentals of Computing I Slide 5 - 6 Operators • Equality and Relational Operators (review): Evaluate to true or false Have lower precedence than arithmetic operators Operator Meaning == equal to != not equal to < less than > greater than <= less than or equal to >= greater than or equal to
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COMP 1210 – Fundamentals of Computing I Slide 5 - 7 Operators
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05_Conditionals_and_Loops - 5. Conditionals and Loops...

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