This trace uses the technique demonstrated in tracing recursive methods and some of the material from the more complex stack based trace with nested recursive calls. Familiarity with the material from those resources is assumed, including the notation.

The same trace is available with each step on its own page, starting with Step 1.

Step 1: initial call

Initial call stack

g("today", 1)

Step 2: goAgain("today", 1)

• Checks if 1 >= 5, which is false
• Computes "today" + ____ (something unknown)
• Calls goAgain with "today".substring(1), which is "oday", and 1 + 1, which is 2

Resulting call stack

g("oday", 2)
g("today", 1)    "today" + ____

Step 3: goAgain("oday", 2)

• Checks if 2 >= 4, which is false
• Computes "oday" + ____
• Calls goAgain with "oday".substring(2), which is "ay", and 2 + 1, which is 3

Resulting call stack

g("ay", 3)
g("oday", 2)     "oday" + ____
g("today", 1)    "today" + ____

Step 4: goAgain("ay", 3)

• Checks if 3 >= 2, which is true
• Stops and returns "ay"

Resulting call stack

g("ay", 3)  returns "ay"
g("oday", 2)     "oday" + ____
g("today", 1)    "today" + ____

Step 5: Back in goAgain("oday", 2)

• Back in goAgain("oday", 2)
• Finished the recursive call, got back "ay"
• Computes "oday" + "ay", which is "odayay"
• Stops and returns "odayay"

Resulting call stack

g("ay", 3)  returns "ay"
g("oday", 2)     "oday" + "ay"  returns "odayay"
g("today", 1)    "today" + ____

Step 6: Back in goAgain("today", 1)

• Back in goAgain("today", 1)
• Finished the recursive call, got back "odayay"
• Computes "today" + "odayay", which is "todayodayay"
• Stops and returns "todayodayay"

Resulting call stack

g("ay", 3)  returns "ay"
g("oday", 2)     "oday" + "ay"  returns "odayay"
g("today", 1)    "today" + "odayay"  returns "todayodayay"