Loops and Logic - Beginning Java - page 99

Although testing characters using logical operators is a useful way of demonstrating how these operators
work, in practice there is an easier way. The standard Java packages provide a range of standard methods to
do the sort of testing for particular sets of characters such as letters or digits that you have been doing with
if statements. They are all available within the Character class, which is automatically available in your
programs. For example, you could have written the if statement in the LetterCheck2 program as shown in
the following example.
TRY IT OUT: Deciphering Characters Trivially
In the following example, the if expressions in main() that were in the LetterCheck2 class have been
replaced by expressions that call methods in the Character class to do the testing:
import static java.lang.Character.isLowerCase;
import static java.lang.Character.isUpperCase;
public class LetterCheck3 {
public static void main(String[] args) {
char symbol = 'A';
symbol = (char)(128.0*Math.random()); // Generate a random
character
if(isUpperCase(symbol)) {
System.out.println("You have the capital letter " + symbol);
} else {
if(isLowerCase(symbol)) {
System.out.println("You have the small letter " + symbol);
} else {
System.out.println("The code is not a letter");
}
}
}
}
LetterCheck3.java
How It Works
Because you have the import statements for the isUpperCase and isLowerCase method names at the
beginning of the source file, you can call these methods without using the Character class name as qual-
ifier. The isUpperCase() method returns true if the char value that you pass to it is uppercase, and
false if it is not. Similarly, the isLowerCase() method returns true if the char value you pass to it is
lowercase.
Table 3-3 shows some of the other methods included in the Character class that you may find useful
for testing characters. In each case, you put the argument of type char that is to be tested between the
parentheses following the method name.