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AP Computer Science A Textbook

1. Primitive Types

2. Using Objects

3. Boolean Expressions and if Statements

3.1 Boolean Expressions

3.2 if Statements and Control Flow

3.3 if-else Statements

3.4 else if Statements

if/else/else if Statements

Add Tip

Add Tip - 8 or 4 Customers

Add Tip - 8, 4, 2 Customers

Check Your Understanding

Exercise: Salmon Spawn

3.5 Compound Boolean Expressions

3.6 Equivalent Boolean Expressions

3.7 Comparing Objects

4. Iteration

5. Writing Classes

6. Arrays

7. ArrayLists

8. 2D Arrays

9. Inheritance

10. Recursion

Chapter 3

Boolean Expressions and if Statements

3.4 else if Statements

Building on the previous two sections, you are going to look at adding the else if clause to our if blocks. The else if clause allows for a multi-way selection by using different conditional statements to represent different conditions.

if/else/else if Statements

You can add the else if keyword between your if and your else statement. If boolean expression one evaluates to false, then boolean expression two gets evaluated next. If boolean expression two also turns out to be false, the code within the else segment will run.

if (boolean expression one) {
   // Segment of code that will run if boolean expression one is true
}
else if (boolean expression two) {
   // Segment of code that will run if boolean expression one is false and two is true
}
else {
   // Segment of code that will run if boolean expression one and boolean expression two are both false
}
Plain text

In the example above, notice how only one condition is executed. With x at 19, it executes the first block of code. Even though x is also less than 30, that block of code is skipped since only one block is executed. After the if clause is executed all other clauses are skipped.

It is important to note that you can have as many else if statements as you want, or you can have none. When looking at conditional blocks of code, the only required statement is the if statement. This can optionally be followed with any number of else if statements, and then optionally one else statement.

Add Tip

Add Tip - 8 or 4 Customers

Add Tip - 8, 4, 2 Customers

Check Your Understanding

  1. Incorrect Correct No Answer was selected Invalid Answer

    What is the output of the following code snippet?

    double ticketPrice = 15.75;

if(ticketPrice > 15)
{
   System.out.println("Too expensive!");
}
if(ticketPrice > 10)
{
   System.out.println("Typical");
}
else if(ticketPrice > 5)
{
   System.out.println("Great deal!");
}
else 
{
    System.out.println("Must be a scam");
}
    Plain text

Exercise: Salmon Spawn

Every year, salmon return from the saltwater they usually live in a freshwater river to spawn (lay eggs). Some people like to go and watch the salmon swim upstream to their favorite spawning places, especially at fish farms.

There are several different varieties of salmon. Some spawn in the spring and most spawn in the fall.

Your task is to write a program that takes the month of the year as an integer and output if it is “Spring spawning season”, “Fall spawning season”, or “Not spawning season”.

The spring spawning season lasts from April to June (months 4- 6). The fall spawning season lasts from October to December (months 10 - 12).

Remember that in an if-else if statement, the first statement that evaluates to true is the one whose body is executed. Therefore, you will need to check the months in numerical order.