RECURSION - Introduction to Java Programming: Comprehensive Version - page 708

factorial(4)

Step 0: executes factorial(4)

Step 9: return 24

return 4 * factorial(3)

Step 1: executes factorial(3)

Step 8: return 6

return 3 * factorial(2)

Step 2: executes factorial(2)

Step 7: return 2

return 2 * factorial(1)

Step 3: executes factorial(1)

Step 6: return 1

return 1 * factorial(0)

Step 4: executes factorial(0)

Step 5: return 1

return 1

F IGURE 18.2

Invoking factorial(4) spawns recursive calls to factorial .

Activation record
for

5

factorial(0)
n: 0

Activation record
for

4 Activation record

for

factorial(1)
n:

factorial(1)
n:

1

1

Activation record
for

Activation record
for

3 Activation record

for

factorial(2)
n:

factorial(2)
n:

factorial(2)
n:

2

2

2

Activation record
for

Activation record
for

Activation record
for

Activation record
for

2

factorial(3)
n:

factorial(3)
n:

factorial(3)
n:

factorial(3)
n:

3

3 3

3

Activation record
for

Activation record
for

Activation record
for

Activation record
for

1 Activation record

for

factorial(4)
n:

factorial(4)
n:

factorial(4)
n:

factorial(4)
n:

factorial(4)
n:

4

4 4 4

4

6 Activation record

for factorial(1)

n: 1

Activation record
for

Activation record
for

7

factorial(2)
n:

factorial(2)
n:

2

2

Activation record
for

Activation record
for

Activation record
for

8

factorial(3)
n:

factorial(3)
n:

factorial(3)
n:

3 3

3

Activation record
for

Activation record
for

Activation record
for

Activation record
for

9

factorial(4)
n:

factorial(4)
n:

factorial(4)
n:

factorial(4)
n:

4 4

4

4

F IGURE 18.3

When factorial(4) is being executed, the factorial method is called recursively, causing stack
space to dynamically change.