What are some decisions we make as human beings?

How do we get the computer to make a decision?

What is the format of an if statement?

 
int grade = 75;

final int PASSING_GRADE = 70;

if (grade >= PASSING_GRADE)
  
  System.out.println("You passed!");













What is the format of an if-else statement?

int grade = 75;

final int PASSING_GRADE = 70;

if (grade >= PASSING_GRADE)
  
  System.out.println("You passed!");

else
  
  System.out.println("You did not pass:(");

What if we want to do more than one thing if a condition is true/not true?

int grade = 75;

final int PASSING_GRADE = 70;

if (grade >= PASSING_GRADE) {
  System.out.println("You passed!");
  System.out.println("Let's go out and celebrate!");
}

else {
  System.out.println("You did not pass:(");
  System.out.println("Please try again");
}

What happens when we try the in-class exercise?
How can we fix it?
 










 		









 		
How could we use "nested" if-else statements to figure out the price of a movie ticket?
 
  Before 6:00 pm      6:00 pm or later

  Under 12  $3.00          $5.50  

12 and over $4.50          $7.00

Assume we have defined and given a value to:

a boolean variable named   beforeSix

an int variable named      age










 		













 
Switch Statements 
What is the format of a switch statement?
 

















 		

    //Print the word for the value where value is 1, 2, or 3
  
    int value = 2;

    switch (value) {
  
      case 1: System.out.println("one");
              break;
	    
      case 2: System.out.println("two");
              break;
	    
      case 3: System.out.println("three");
              break;
	    
      default: System.out.println("Invalid value: " + value);
    }








    //Print the word for the gender 
    //when abbreviated as 'M', 'm', 'F', or 'f' 
  
    char gender = 'm';
  
    switch (gender) {
  
      case 'M':
      case 'm': System.out.println("male");
                break;
	      
      case 'F':
      case 'f': System.out.println("female");
                break;
	      
      default: System.out.println("Invalid gender: " + gender);
    }
    
    //Illustrate dropping through to the next case 
    //with "Twelve Days of Christmas"
    //but only do 5 days, since I'm not about to 
    //type in all twelve days
    
    int day = 4;
    
    switch (day) {
      
      case 5: System.out.println("Five golden rings");
      case 4: System.out.println("Four calling birds");
      case 3: System.out.println("Three French hens");
      case 2: System.out.println("Two turtle doves");
      case 1: System.out.println("And a partridge in a pear tree");
              break;
      
      default: System.out.println("Invalid day: " + day);
    }














Conditional Operator(ADVANCED)

    final int PASSING_SCORE = 60;
    
    //Use conditional operator to compare score to passing score and
    //print "Passed" or "Failed"
    
    int score = 65;
    
    System.out.println( score >= PASSING_SCORE ? "Passed" : "Failed");
    
    //Use conditional operator to set grade to 'S' or 'U', based on score
    
    char grade;
    
    grade = (score >= 60) ? 'S' : 'U';
    
    System.out.println("Grade: " + grade);
    
    int x = 5, y = 10, z = 10;

Short Circuit Operators
What do mean when we say that && and || are "short-circuit" operators?
    
   
    //Ilustrate  "short-circuit operator" && 
    
    int x = 6;
    int y = 9;
    int z = 7;
    
    System.out.println( x == y && (y = 8) < z );
    
    System.out.println("y = " + y);
    
    
    //Illustrate "short-circuit operator" || 
    
    x = 3;
    
    
    System.out.println( x < y || (y = 5) < z);
    
    System.out.println("y = " + y);
    
    
    
    
   
What is the "dangling-else problem"? Which if statement does the else belong with in the code below?
 
    boolean isHot = true;
    boolean isRaining = false;
    
    if (isHot)
    
      if (!isRaining)
      
        System.out.println("Go swimming!!");

      else
      
        System.out.println("It's hot, but too rainy to swim");






How can we fix the code below?
    
    
    isHot = false;	
    
    if (isHot)
    
      if (isRaining)
      
        System.out.println("Too rainy to swim");
	
    else
    
      System.out.println("It's cold today");