it.ozimov.cirneco.hamcrest.iterable.IsEmptyIterable 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;

/**
 * Is the {@linkplain Iterable} empty?
 * 
 * The matcher first checks if the given {@code Iterable} is a
 * {@linkplain Collection} (to get some speedup by using the {@linkplain Collection#isEmpty()}} method, otherwise
 * get the iterator from the {@code Iterable} and check if has a next item.
 *
 * @since version 0.1 for JDK7
 */
public class IsEmptyIterable extends TypeSafeMatcher> {

    /**
     * Creates a matcher for {@link Iterable}s that matches when the
     * examined {@link Iterable} has no items.
     * 

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

    @Override
    public boolean matchesSafely(final Iterable actual) {
        if (actual instanceof Collection) {
            return ((Collection) actual).isEmpty();
        } else {
            return !actual.iterator().hasNext();
        }
    }

    @Override
    public void describeMismatchSafely(final Iterable actual, final Description mismatchDescription) {
        mismatchDescription.
                appendValueList("[", ", ", "]", actual);
    }

    @Override
    public void describeTo(final Description description) {
        description.appendText("an empty iterable");
    }
}