Java puzzlers

This week I attended the very first and very well organized conference What’s Next ? in Paris and one of the speakers was Neil Gafter, co-author of the book “Java™ Puzzlers: Traps, Pitfalls, and Corner Cases” (2005).
He shared with us 2 or 3 puzzlers which I will share here too :
Question 1) What will the following program print ?

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(2)) {
            case 1: word = new StringBuffer('P');
            case 2: word = new StringBuffer('G');
            default: word = new StringBuffer('M');
        }
        word.append('a');
        word.append('i');
        word.append('n');
        System.out.println(word);
    }
}

1) Pain
2) Gain
3) Main
4) ain

Answer :
It does not print Pain, Gain or Main ! It always prints ain ! There are 3 bugs in this program.
A few explanations :
a) The only possible values of the expression rnd.nextInt(2) are 0 and 1
b) remember “break” in “switch” element !
c) new StringBuffer(‘M’) ==> it’s actually the new StringBuffer(int) constructor which is used !

A corrected version is :

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;
        }
        word.append('a');
        word.append('i');
        word.append('n');
        System.out.println(word);
    }
}

Question 2) What does the following program print ?

public class Elementary {
    public static void main(String[] args) {
        System.out.println(12345 + 5432l);
    }
}

1) 66666
2) 17777

Answer : 17777
Explanation :

5432l

is actually a long, not an int.

l

is the lowercase letter el, it is not the digit 1.
So a good practice is to use capital el (L) in long literals, not a lowercase el (l) :

System.out.println(12345 + 5432L);