Conditional Execution - Building Java Programs: A Back to Basics Approach - page 256

Table 4.5 Useful Methods of the Character Class

Method Description Example

Converts a character that looks

getNumericValue(ch) Character.getNumericValue('6')

like a number into that number returns 6

Whether or not the character is

isDigit(ch) Character.isDigit('X')

one of the digits '0' through '9' returns false

Whether or not the character is in

isLetter(ch) Character.isLetter('f')

the range 'a' to 'z' or 'A' to 'Z' returns true

Whether or not the character is a

isLowerCase(ch) Character.isLowerCase('Q')

lowercase letter returns false

Whether or not the character is an

isUpperCase(ch) Character.isUpperCase('Q')

uppercase letter returns true

The lowercase version of the given

toLowerCase(ch) Character.toLowerCase('Q')

letter returns 'q'

The uppercase version of the given

toUpperCase(ch) Character.toUpperCase('x')

letter returns 'X'

concatenating individual characters in the loop. This is called a cumulative concate-
nation . The following method accepts a string and returns the same characters in the
reverse order:

public static String reverse(String phrase) {
String result = "";
for (int i = 0; i < phrase.length(); i++) {
result = phrase.charAt(i) + result;

}
return result;

}

For example, the call of reverse("Tin man") returns "nam niT" .
Several useful methods can be called to check information about a character or
convert one character into another. Remember that char is a primitive type, which
means that you can't use the dot syntax used with String s. Instead, the methods are
static methods in a class called Character ; the methods accept char parameters and
return appropriate values. Some of the most useful Character methods are listed in
Table 4.5.
The following method counts the number of letters A-Z in a String , ignoring all
nonletter characters such as punctuation, numbers, and spaces:

public static int countLetters(String phrase) {
int count = 0;
for (int i = 0; i < phrase.length(); i++) {
char ch = phrase.charAt(i);