Dan Chisholm's question from chapter 5

[Sarbani Mookherji]

Can any please give an explanation to the answer of this question:
class Black {
public static void main (String args[]) {
int i = 0;
int j = 0;
label1:
while (i++<5) {
label2:
for (; {
label3:
do {
System.out.print(i + j);
switch (i+j++) {
case 0: continue label3;
case 1: continue label2;
case 2: continue label1;
case 3: break;
case 4: break label3;
case 5: break label2;
case 6: break label1;
default: break label1;
}
} while (++j<5);
}
}
}
}

What is the result of attempting to compile and run the above program?
a. Prints: 12457
b. Prints: 02357
c. Prints: 02356
d. Prints: 1357
e. Prints: 1356
f. Runtime Exception
g. Compiler Error
h. None of the Above
Answer given is a.

[Jose Botella]

Welcome to the Ranch Sarbani. Please see below the link "What is UBB Code?" to ident properly your code.

public static void main (String args[]) {
int i = 0;
int j = 0;
label1:
while (i++<5) {//A
label2:
for (; ; )  {//B
label3:
do {
System.out.print(i + j);//C
switch (i+j++) {//D
case 0: continue label3;
case 1: continue label2;
case 2: continue label1;
case 3: break;
case 4: break label3;
case 5: break label2;
case 6: break label1;
default: break label1;
}
} while (++j<5); //E
}
}
}

1)i=0,j=0
2)after point A i=1
3)C prints 1
4)D evalutes to continue label 2. Independently of that j=1 after D
5)continue label 2 will break E, that is, j is still 1. If B had gotten an increment expression it would have been executed.
6)C prints 2
7)D evalutes to continue label 1. After D j=2
8)continue label 1 will break E again, that is, "++j<5" is not executed. If A had gotten an increment expression it would have been executed before "i++<5".
9)In A 1<5 and i=2 after A
10)C prints 4
11)D evalutes to break label 3. After D j=3
12)break label 3 breaks E and the next B iteration begins
13)C prints 5
14)D evaluates to break label 2. After D j=4
15)break label 2 breaks E and B. The next A iteration begins. If A had gotten an increment expression it would have been executed before "i++<5"
16)in A 2<5 and after A i=3
17)C prints 7
18)D evaluates to default. After D j=5
19)break label 1 jumps out of A ending the program.
Hope it helps.
[ March 23, 2003: Message edited by: Jose Botella ]