RECURSION - Java Programming: From Problem Analysis to Program Design - page 890

The following recursive method implements this algorithm:

public static void decToBin( int num, int base)
{

if (num == 0)
System.out.print(0);
else if (num > 0)
{

decToBin(num / base, base);
System.out.print(num % base);

}

}

Figure 13-8 traces the execution of the following statement:

decToBin(13, 2);
where num is 13 and base is 2 .

decToBin(13,2)
num base

13 2

execute
System.out.print(13 % 2);

Call 1

because num > 0
decToBin(13/2,2);
decToBin(6,2)
num base

Output: 1

execute
System.out.print(6 % 2);

6 2

Call 2

because num > 0
decToBin(6/2,2);

Output: 0

decToBin(3,2)
num base

execute
System.out.print(3 % 2);

3 2

Call 3

because num > 0
decToBin(3/2,2);
decToBin(1,2)
num base

Output: 1

execute
System.out.print(1 % 2);

1 2

Call 4

because num > 0
decToBin(1/2,2);
decToBin(0,2)
num base

Output: 1

0 2

Call 5

because num is 0
exit this call

FIGURE 13-8 Execution of decToBin(13, 2)

Because the if statement in Call 5 succeeds, this call prints 0 . The second output is
produced by Call 4, which prints 1 ; the third output is produced by Call 3, which