Introduction to Computer Programming

1
Introduction to Computer Programming

• CS 126
• Lecture 7
• Zeke Maier

2
Plan for Today

• Questions
• Administrivia
• Conditionals
• AD Exercises 4.2 4.3
• Assignment

3
Questions
4
Administrivia

• http//students.cec.wustl.edu/ejm3/
• Lab assignment 1 due this afternoon!
• Lab assignment 2 assigned today

5
Conditional Statements

• Allows us to change the behavior of the program
  based on certain conditions
• Example absolute value

If (condition) //Statements to execute if the
condition is true
else //Statements to execute if the
condition is false
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Conditionals

• Write a method producing the same output (y
  values) given the same input (x values) as the
  function below

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Chained Conditionals

• Useful when there are more than 2 discrete cases?

if (condition) //Statements to execute if the
condition is true else if() //Statements
else if() //Statements else //Statements
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Example
if (x gt 0) System.out.println(1) else if(
x 7) System.out.println(2) else
if(false) System.out.println(3) else
if(xlt0 x gt -100) System.out.println(4)
else System.out.println(5)
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Nested Conditionals
If (condition) if (condition2) //Statements
else //Statements else
//Statements

• How would you write a conditional to determine if
  a year was a leap year?

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Shortening Conditionals

• If the body of the conditional is a single line,
  then braces () are not needed.
• Avoid using a conditional just to return the
  value of a test
• Do not write unnecessary else conditions

if (condition) return condition return
true else return false
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AD Exercises 4.2 4.3

• http//students.cec.wustl.edu/ejm3/CS126/web/code
  .htmlconditionals

12
Assignments

• Lab 1 due today!
• Lab 2 assigned today
• Readings
• Friday
• AD Appendix A B
• KG Notes