CSE110 Lecture 08

CSE110 Lecture 08

Principles of Programming with Java
Conditional Statements
(202005)

B546a9b97d993392e4b22b74b99b91fe?s=128

Javier Gonzalez

May 26, 2017
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  1. CSE110 Principles of Programming with Java Lecture 08: Conditional Statements

    Javier Gonzalez-Sanchez javiergs@asu.edu javiergs.engineering.asu.edu | javiergs.com Office Hours: By appointment
  2. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 2 Announcement

    Assignment 1 is due today (11:59 PM AZ Time) Midterm Exam (Monday June 8, 6:00PM to 7:15PM AZ time)
  3. Previously

  4. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 4 Input

  5. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 5 Input

    import javax.swing.JOptionPane; public class Lecture06 { public static void main(String [] args) { String test1= JOptionPane.showInputDialog(”write here:"); int value1 = Integer.parseInt(test1); double value2 = Double.parseDouble(test1); System.out.println(value1); System.out.println(value2); } }
  6. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 6 Expressions

    class global variables methods statements local variables instructions expressions arithmetic expression relational expression logical expression
  7. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 7 Relational

    expressions A condition uses relational operators, which all return boolean results: == equal to != not equal to < less than > greater than <= less than or equal to >= greater than or equal to Note the difference between the equality operator (==) and the assignment operator (=)
  8. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 8 Boolean

    (logical) expressions A condition uses relational operators, which all return boolean results: && AND || OR ! NOT
  9. Control Statements

  10. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 10 Topics

    class global variables methods statements instructions local variables expressions
  11. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 11 Topics

    class global variables methods statements instructions local variables expressions conditional Statements loop Statements
  12. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 12 Flow

    of Control Unless specified otherwise, the order of statement execution through a method is linear: one statement after the other in sequence (top down order). public static void main (String [] args) { System.out.println(“one”); System.out.println(“two”); System.out.println(“three”); } The order of statement execution is called the flow of control
  13. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 13 Flow

    of Control Some programming statements modify that order (flow of control), allowing us to: • decide whether to execute a statement, or • perform a statement over and over, repetitively These decisions are based on a boolean expression (also called a condition) that evaluates to true or false.
  14. Conditional Statements

  15. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 15 Conditional

    Statements • A conditional statement lets us choose which statement will be executed next • Java's conditional statements are o the if statement o the if-else statement o the switch statement o the operator ?
  16. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 16 if

    statement • The if statement has the following syntax:
  17. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 17 Example

    int MAX = 5; int sum = 30; int delta = 0; if (sum > MAX) { delta = sum - MAX; } System.out.println("The delta is " + delta);
  18. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 18 Flow

    Chart of an if statement
  19. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 19 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
  20. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 20 Flow

    chart of an if-else statement
  21. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 21 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
  22. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 22 if-else

    if-else You can also have multiple conditions to be verified: 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!"); }
  23. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 23 if-else

    if-else The code from the previous page is equivalent to: 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!"); } } }
  24. Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 24 Reference

    Textbook – Section 3.1, 3.2, and 3.3
  25. 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.