Tracing recursion | Together Java | Page 1

visual shore Feb 23, 2026, 7:01 PM

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How do I trace this I get really confused

weary basinBOT Feb 23, 2026, 7:01 PM

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<@&987246399047479336> please have a look, thanks.

fleet path Feb 23, 2026, 7:02 PM

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pen and paper

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play "dumb java robot", executing the code step by step by hand

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its to demystify recursion. to show u that recursion is no magic at all and that java simple executes a method when being told to execute one

visual shore Feb 23, 2026, 7:28 PM

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fleet path play "dumb java robot", executing the code step by step by hand

how please

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stacking method

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like how would you do it

wind compass Feb 23, 2026, 7:30 PM

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dosomething gets called with 3, so what does it do?

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0 won't work, so let's say that 1 is the last number that does anything
1 prints just 1 as both calls to dosomething when the argument is 1, turns those into 0, which we just said doesn't do anything

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dosomething 2
 bigger than 0, yes
 dosomething 1
  bigger than 0, yes
  print 1
 print 2
 dosomething 1
  bigger than 0, yes
  print 1

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So dosomething 2 has 3 prints

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first one prints 1, then 2, then 1 again

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so the output for dosomething 2 is 121

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Then the output for dosomething 3 is dosomething2 twice, with a 3 in between

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So the output is 1213121

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dosomething 4 would be 121312141213121

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etc

fleet path Feb 23, 2026, 7:40 PM

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visual shore how please

as said, just execute the code step by step with pen and paper

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like, literally

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dont try to be smart about it

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just do it and it will be crystal clear

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doSomething(3) starts. what is the very first thing that happens?

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whats the first thing in the method

visual shore Feb 23, 2026, 7:41 PM

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check condition, n>3

fleet path Feb 23, 2026, 7:42 PM

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yes. n is 3. so its true

visual shore Feb 23, 2026, 7:42 PM

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doSomething(2)

fleet path Feb 23, 2026, 7:42 PM

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it enters the if

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now it says doSomething(2)

visual shore Feb 23, 2026, 7:42 PM

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Yes

fleet path Feb 23, 2026, 7:42 PM

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so. java has to call a method

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that means it has to pause the current method and park it

visual shore Feb 23, 2026, 7:42 PM

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OH

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Ok

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Now

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n is 2

fleet path Feb 23, 2026, 7:42 PM

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so. now we start doSomething(2)

visual shore Feb 23, 2026, 7:42 PM

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2>0 yes

fleet path Feb 23, 2026, 7:42 PM

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yes

visual shore Feb 23, 2026, 7:42 PM

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doSomething(1)

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stop everything and call doSomething(1)

fleet path Feb 23, 2026, 7:43 PM

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yes. so doSomething(2) needs to be paused now

visual shore Feb 23, 2026, 7:43 PM

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1>0 yes

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doSomething(0), does not enter if

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now where do i go

fleet path Feb 23, 2026, 7:43 PM

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the method is done. so java goes back to who called it and resumes that paused method

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who called it? it was doSomething(1)

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so we continue there now

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where did it pause? inside the if, at that doSomething(0)

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so whats the next statement

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to java its just method calls. it doesnt know anything about recursion, its "dumb". it just plays the normal java rules step by step

visual shore Feb 23, 2026, 7:45 PM

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peepo_happy

fleet path Feb 23, 2026, 7:45 PM

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a method calls a method, pause it.
a method is done, go back to who called it.

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easy 🙂

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and now its just continuing with it step by step until ur done

#Tracing recursion