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Magical Java Puzzle: Pat the unicorns
/** See: http://zeroturnaround.com/fun/magical-java-puzzle-pat-the-unicorns/ */
import java.util.*;
public class Unicorn {
static Set<Integer> lines = new HashSet<Integer>();
public static boolean pat() {
int callerLine = Thread.currentThread().getStackTrace()[3].getLineNumber();
return lines.add(callerLine);
}
}
/**
* When called by the following program:
<code>
public class MagicalLand {
public static void main(String[] args) {
for (int i = 0; i < (Math.random() * 500) + 2; i++) {
if (Unicorn.pat()) {
System.out.println("UNICORN #1: PAT THIS UNICORN ONCE");
}
}
for (int i = 0; i < (Math.random() * 500) + 2; i++) {
if (Unicorn.pat()) {
System.out.println("UNICORN #2: PAT THIS UNICORN ONCE");
}
}
System.out.println("END OF PROGRAM");
}
}
</code>
*
* Will print:
UNICORN #1: PAT THIS UNICORN ONCE
UNICORN #2: PAT THIS UNICORN ONCE
END OF PROGRAM
*/
@jodem

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jodem commented Mar 15, 2013

That's an elegant solution :)

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