it.ozimov.cirneco.hamcrest.iterable.IsIterableWithDistinctElements Maven / Gradle / Ivy

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package it.ozimov.cirneco.hamcrest.iterable;

import org.hamcrest.Description;
import org.hamcrest.Matcher;
import org.hamcrest.TypeSafeMatcher;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

import static it.ozimov.cirneco.hamcrest.iterable.utils.IterableUtils.listCopy;
import static it.ozimov.cirneco.hamcrest.iterable.utils.IterableUtils.size;

/**
 * Is the {@linkplain Iterable} with distinct elements?
 * 
 * To verify that only distinct elements are in the {@code Iterable},
 *
 * @since version 0.2 for JDK7
 */
public class IsIterableWithDistinctElements extends TypeSafeMatcher> {

    /**
     * Creates a matcher for {@link Iterable}s that matches when the
     * examined {@link Iterable} has only distinct elements.
     * 

     * For example:
     * 
assertThat(new ArrayList<>(), empty())
     * returns true.
     */
    public static  Matcher> hasDistinctElements() {
        return new IsIterableWithDistinctElements<>();
    }

    @Override
    public boolean matchesSafely(final Iterable actual) {
        return new HashSet<>(listCopy(actual)).size() == size(actual);
    }

    @Override
    public void describeMismatchSafely(final Iterable actual, final Description mismatchDescription) {
        final Collection collection = listCopy(actual);
        final Set elements = new HashSet<>(collection);
        final Set nonDistinctElements = new HashSet<>();
        for (final E element : elements) {
            if (Collections.frequency(collection, element) > 1) {
                nonDistinctElements.add(element);
            }
        }

        mismatchDescription.appendText(" non distinct elements are ").
                appendValueList("[", ", ", "]", nonDistinctElements);
    }

    @Override
    public void describeTo(final Description description) {
        description.appendText("an iterable with all distinct elements");
    }
}