The Conditional Operator and the 'switch' Statement
Read this chapter, which discusses the switch and '?' operators to write conditional statements. As you read this tutorial, you will learn that sometimes it is better to use a 'switch' statement when there are multiple choices to choose from. Under such conditions, an if/else structure can become very long, obscure, and difficult to comprehend. Once you have read the tutorial, you will understand the similarity of the logic used for the 'if/else' statement, '?', and 'switch' statements and how they can be used alternately.
13. Range Testing
Answer:
There is nothing wrong with the program. Since color is a primitive data type, an expression such as
color == 'V'
compares the contents of color (a character) to the character literal 'V'. However, the following is wrong:
color == "V"
This is asking to compare the primitive character value in color with a reference to the String object "V".
Range Testing
Say that you have the following problem: Assign a Beaufort number to bNumber based on wind speed in meters per second.
wind speed |
Beaufort number |
|---|---|
0 - 0.3 |
0 |
0.3 - 1.6 |
1 |
1.6 - 3.4 |
2 |
3.4 - 5.5 |
3 |
5.5 - 8.0 |
4 |
8.0 - 10.8 |
5 |
10.8 - 13.9 |
6 |
13.9 - 17.2 |
7 |
17.2 - 20.8 |
8 |
20.8 - 24.5 |
9 |
24.5 - 28.5 |
10 |
28.5 - 32.7 |
11 |
>=32.7 |
12 |
Assume that the upper number in each range is not included.
Lots of cases! You would hope that the switch statement would work for this. But it does not. Floating point values don't work with switch statements. You need to use if and else if.
if ( speed < 0.3 ) bNumber = 0; else if ( speed < 1.6 ) bNumber = 1; else if ( speed < 3.4 ) bNumber = 2; else if ( speed < 5.5 ) bNumber = 3; else if ( speed < 8.0 ) bNumber = 4; else if ( speed < 10.8 ) bNumber = 5; else if ( speed < 13.9 ) bNumber = 6; else if ( speed < 17.2 ) bNumber = 7; else if ( speed < 20.8 ) bNumber = 8; else if ( speed < 24.5 ) bNumber = 9; else if ( speed < 28.5 ) bNumber = 10; else if ( speed < 32.7 ) bNumber = 11; else bNumber = 12; |
Question 13:
Could integer ranges be used with a switch statement? Say that value is expected to be in
the range 1..10 and you want three categories: 1 to 3, 4 to 7, 8 to 10.