So you think you know Java...

Main.java

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.ref.WeakReference;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Random;
import java.util.function.IntFunction;
import java.util.function.Supplier;
import java.util.stream.IntStream;

// This code prints, at random, "even" or "odd" to either System in or System out.
// It also has a subtle race condition.

public class Main {

	@Retention(RetentionPolicy.RUNTIME)
	public @interface target {
		String value();
	}
	
	public String callIfEven() {
		return Thread.currentThread().getStackTrace()[1].getMethodName().substring(6).toLowerCase();
	}

	@target(value = "odd")
	public String callIfOdd() {
		try {
			return getClass()
					.getMethod(Thread.currentThread().getStackTrace()[1].getMethodName())
					.getAnnotation(target.class)
					.value();
		} catch (NoSuchMethodException | SecurityException e) {
			return null;
		}
	}

	public int modulo2(int x) {
		return (IntStream.range(0, x).reduce((a, b) -> (a == 0 ? 1 : 0)).getAsInt() == 0 ? 1 : 0);
	}

	public static void main(String[] args) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		Random r = new Random();
		Main m = new Main();

		Method out = System.out.getClass().getMethod("println", String.class);

		WeakReference<Method> wr = new WeakReference<Method>(out);
		
		for (int i = 0; i < 1000; i++) {
			int[] ary = new int[1000];
			ary[i] = 5;
		}
		
		out = (wr.get() == null ? out : wr.get());
		
		out.invoke((r.nextInt() % 2 == 0 ? System.out : System.err), 
				(((IntFunction<Integer>) m::modulo2).apply(r.nextInt(100)) == 0 ? 
				((Supplier<String>) m::callIfEven).get() : ((Supplier<String>) m::callIfOdd).get()));


	}

}