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POOccasional StackOverflowError in Recursive Calculation
 

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  1. POOccasional StackOverflowError in Recursive Calculation
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    <p>When executing the code pasted below in Eclipse, approximately 1 out of 3 times I encounter the following exception:</p> <pre><code>Exception in thread "main" java.lang.StackOverflowError at src.Adder.recursiveSumAllNumbersUpTo(Driver.java:33) at src.Adder.recursiveSumAllNumbersUpTo(Driver.java:37) ... *(there are 1024 lines in this stack)* </code></pre> <p>The other 2 times, it spits out the result as intended (the times vary slightly between each run):</p> <pre><code>Recursive: 467946 Non Recursive: 61282 Difference between recursive and non-recursive: 406664 Sum from recursive add: 19534375 Sum from non-recursive add: 19534375 </code></pre> <p>Why does the exception only happen (seemingly) ~30% of the time?</p> <p>Here's the code:</p> <pre><code>public class Driver { public static void main(String[] args) { Adder adder = new Adder(); int valueToSumTo = 6250; long startTime = System.nanoTime(); int raSum = adder.recursiveAddAllNumbersUpTo(valueToSumTo); long endTime = System.nanoTime(); long raDif = endTime - startTime; System.out.println("Recursive: " + (raDif)); startTime = System.nanoTime(); int nonRaSum = adder.nonRecursiveAddAllNumbersUpTo(valueToSumTo); endTime = System.nanoTime(); long nonRaDif = endTime - startTime; System.out.println("Non Recursive: " + (nonRaDif)); System.out.println("Difference between recursive and non-recursive: " + (raDif - nonRaDif)); System.out.println("Sum from recursive add: " + raSum); System.out.println("Sum from non-recursive add: " + nonRaSum); } } class Adder { public int recursiveAddAllNumbersUpTo(int i) { if (i == 1) { return i; } return i + recursiveAddAllNumbersUpTo(i - 1); } public int nonRecursiveAddAllNumbersUpTo(int i) { int count = 0; for(int num = 1; num &lt;= i; num++) { count += num; } return count; } } </code></pre>
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