Recursion - Java - page 598

EXAMPLE:

(continued)

The following is the complete code for the method:

public static void writeVertical( int n)
{
if (n < 10)
{
System.out.println(n);
}
else //n is two or more digits long:
{
writeVertical(n/10);
System.out.println(n%10);
}
}

Tracing a Recursive Call

Let's see exactly what happens when the following method call is made (as in Display 11.1):

writeVertical(123);

When this method call is executed, the computer proceeds just as it would with any method
call. The argument is substituted for the parameter and the body of the method is exe-

123 n

cuted. After the substitution of for , the code to be executed is equivalent to

123 n

if (123 < 10)
{
System.out.println(123);
}
else //n is two or more digits long:
{
writeVertical(123/10);
System.out.println(123%10);
}

Computation will stop here
until the recursive call
returns.

Since is not less than , the part is executed. However, the part begins

123 10 else else

with the method call

writeVertical(n/10);