Puzzlers with Character - Java Puzzlers: Traps, Pitfalls, and Corner Cases - page 60

The last and most subtle bug is that the expression new StringBuffer('M') probably does not do
what you think it does. You may not be familiar with the StringBuffer(char) constructor, and
with good reason: It does not exist. There is a parameterless constructor, one that takes a String
indicating the initial contents of the string buffer and one that takes an int indicating its initial
capacity. In this case, the compiler selects the int constructor, applying a widening primitive
conversion to convert the char value 'M' into the int value 77 [JLS 5.1.2]. In other words, new
StringBuffer('M') returns an empty string buffer with an initial capacity of 77. The remainder of
the program appends the characters a , i , and n to the empty string buffer and prints out its contents,
which are always ain .
To avoid this kind of problem, use familiar idioms and APIs whenever possible. If you must use
unfamiliar APIs, read the documentation carefully. In this case, the program should have used
the common StringBuffer constructor that takes a String .
This corrected version of the program fixes all three bugs, printing Pain , Gain , and Main with equal
likelihood:
import java.util.Random;
public class Rhymes {
private static Random rnd = new Random();
public static void main(String[] args) {
StringBuffer word = null;
switch(rnd.nextInt( 3 )) {
case 1:
word = new StringBuffer( "P" );
break;
case 2:
word = new StringBuffer( "G" );
break;
default:
word = new StringBuffer( "M" );
break;