METHODS - Introduction to Java Programming: Comprehensive Version - page 224

As discussed in Section 4.3.3, all numeric operators can be applied to the char operands. The
char operand is cast into a number if the other operand is a number or a character. Therefore,
the preceding expression can be simplified as follows:

'a' + Math.random() * ( 'z' - 'a' + 1 )

and a random lowercase letter is

( char )( 'a' + Math.random() * ( 'z' - 'a' + 1 ))

Hence, a random character between any two characters ch1 and ch2 with ch1 < ch2 can be
generated as follows:

( char )(ch1 + Math.random() * (ch2 - ch1 + 1 ))

This is a simple but useful discovery. Listing 6.10 defines a class named RandomCharacter
with five overloaded methods to get a certain type of character randomly. You can use these
methods in your future projects.

L ISTING 6.10

RandomCharacter.java
1 public class RandomCharacter {
2 /** Generate a random character between ch1 and ch2 */

3 public static char getRandomCharacter( char ch1, char ch2) { getRandomCharacter

4 return ( char )(ch1 + Math.random() * (ch2 - ch1 + 1 ));

5 }
6
7

/** Generate a random lowercase letter */

getRandomLower
CaseLetter()

8 public static char getRandomLowerCaseLetter() {

9 return getRandomCharacter( 'a' , 'z' );

10 }
11
12 /** Generate a random uppercase letter */

13 public static char getRandomUpperCaseLetter() {

getRandomUpper
CaseLetter()

14 return getRandomCharacter( 'A' , 'Z' );

15 }
16
17

/** Generate a random digit character */

18 public static char getRandomDigitCharacter() {

getRandomDigit
Character()

19 return getRandomCharacter( '0' , '9' );

20 }
21
22

/** Generate a random character */

23 public static char getRandomCharacter() {

getRandomCharacter()

24 return getRandomCharacter( '\u0000' , '\uFFFF' );

25 }
26 }

Listing 6.11 gives a test program that displays 175 random lowercase letters.

L ISTING 6.11

TestRandomCharacter.java
1 public class TestRandomCharacter {
2 /** Main method */

3 public static void main(String[] args) {

4 final int NUMBER_OF_CHARS = 175 ; constants

5 final int CHARS_PER_LINE = 25 ;

6
7

// Print random characters between 'a' and 'z', 25 chars per line

8 for ( int i = 0 ; i < NUMBER_OF_CHARS; i++) {