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Jqwik Engine module

There is a newer version: 1.9.1

package net.jqwik.engine.properties.arbitraries.randomized;

import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;

import net.jqwik.api.*;
import net.jqwik.engine.properties.shrinking.*;

public class UniqueGenerator implements RandomGenerator {
	private static final long MAX_MISSES = 10000;
	private final RandomGenerator toFilter;
	private final Set usedValues = ConcurrentHashMap.newKeySet();

	public UniqueGenerator(RandomGenerator toFilter) {
		this.toFilter = toFilter;
	}

	@Override
	public Shrinkable next(Random random) {
		return nextUntilAccepted(random, r -> {
			Shrinkable next = toFilter.next(r);
			return new UniqueShrinkable<>(next, usedValues);
		});
	}

	@Override
	public String toString() {
		return String.format("Unique [%s]", toFilter);
	}

	private Shrinkable nextUntilAccepted(Random random, Function> fetchShrinkable) {
		long count = 0;
		while (true) {
			Shrinkable next = fetchShrinkable.apply(random);
			if (usedValues.contains(next.value())) {
				if (++count > MAX_MISSES) {
					throw new TooManyFilterMissesException(String.format("%s missed more than %s times.", toString(), MAX_MISSES));
				}
				continue;
			} else {
				usedValues.add(next.value());
			}
			return next;
		}
	}

}