CSE110 Lecture 09

Principles of Programming with Java
Nested if-else Statements
(202205)

Transcript

1. CSE110
   Principles of Programming
   with Java
   Lecture 09:
   Nested if-else Statements
   Javier Gonzalez-Sanchez
   javiergs@asu.edu
   javiergs.engineering.asu.edu | javiergs.com
   Office Hours: By appointment
   

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2. if-else
   

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3. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 9
   if-else statement
   An else clause can be added to an if statement to
   make an if-else statement
   if ( condition ) {
   statement1;
   } else {
   statement2;
   }
   • If the condition is true, statement1 is executed; if the
   condition is false, statement2 is executed
   • One or the other will be executed, but not both
   

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4. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 10
   Flow chart of an if-else statement
   

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5. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 11
   Nested if Statements
   • The statement executed as a result of an if
   statement or else clause could be another if
   statement
   • These are called nested if statements
   • An else clause is matched to the last unmatched if
   (no matter what the indentation implies)
   • Braces can be used to specify the if statement to
   which an else clause belongs
   

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6. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 12
   if-else if-else
   if (temp > 100) {
   System.out.println("It is hot!");
   } else {
   if (temp > 80) {
   System.out.println("It is warm");
   } else {
   if (temp > 50){
   System.out.println("It is chilly");
   } else {
   System.out.println("It is cold!");
   }
   }
   }
   

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7. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 13
   Block Statements
   • Several statements are grouped together into a
   block statement
   • A block is delimited by braces: {...}
   • For example, in an if-else statement, the if portion,
   or the else portion, or both, could be block
   statements
   • There is no need to use braces if there is only one
   statement or one set of “if-else” within the outer “if”
   statement
   

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8. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 14
   Block Statements
   

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9. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 15
   if-else if-else
   if (temp > 100) {
   System.out.println("It is hot!");
   } else {
   if (temp > 80) {
   System.out.println("It is warm");
   } else {
   if (temp > 50){
   System.out.println("It is chilly");
   } else {
   System.out.println("It is cold!");
   }
   }
   }
   

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10. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 16
    if-else if-else
    This is the same the the previous one:
    if (temp > 100) {
    System.out.println("It is hot!");
    } else if (temp > 80) {
    System.out.println("It is warm");
    } else if (temp > 50) {
    System.out.println("It is chilly");
    } else {
    System.out.println("It is cold!");
    }
    

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11. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 17
    Logical NOT
    • The logical NOT operation is also called logical
    negation or logical complement
    • If some boolean condition a is true, then !a is false; if
    a is false, then !a is true
    • Logical expressions can be shown using truth tables
    

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12. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 18
    Logical AND and Logical OR
    • Since && and || each have two operands, there
    are four possible combinations of conditions a and
    b
    

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13. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 19
    Logical Operators
    Conditions can use logical operators to form complex
    expressions
    if (total < MAX+5 && !found)
    System.out.println ("Processing...");
    Logical operators have precedence relationships among
    themselves and with other operators
    • The relational or arithmetic operators have higher
    precedence than logical AND and logical OR
    • logical NOT has higher precedence than logical AND.
    Logical AND has higher precedence than logical OR
    

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14. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 20
    Example
    int examGrade = 90;
    int assignmentGrade = 80;
    int quizGrade = 85;
    if (examGrade > 85 && assignmentGrade > 85)
    System.out.println(“Well done!”);
    else if (quizGrade < 70 || assignmentGrade < 85)
    System.out.println(“Houston, we have a problem”);
    

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15. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 21
    Example
    

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16. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 22
    Example
    

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17. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 23
    Reference
    Textbook – Section 3.1, 3.2, and 3.3
    

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18. CSE110 - Principles of Programming
    Javier Gonzalez-Sanchez
    javiergs@asu.edu
    Summer 2020
    Disclaimer. These slides can only be used as study material for the class CSE110 at ASU. They cannot be distributed or used for another purpose.
    

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