MaxValueFromList.java

package com.levelup.java.collections;

import static org.junit.Assert.assertEquals;

import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.OptionalInt;

import org.apache.commons.lang3.ObjectUtils;
import org.junit.Test;

import com.google.common.collect.Lists;
import com.google.common.collect.Ordering;
import com.google.common.primitives.Ints;

/**
 * This java example will demonstrate getting max value from a list.
 * 
 * @author Justin Musgrove
 * @see <a
 *      href='http://www.leveluplunch.com/java/examples/max-value-in-list/'>Max
 *      value in list</a>
 * 
 */
public class MaxValueFromList {

	private static List<Integer> CENTERS_ROOKIE_YEAR = Lists.newArrayList(1946,
			1988, 1970, 1931, 1940, 1920, 1980, 1953, 1960, 1974, 1987);

	@Test
	public void find_max_value_from_list_of_integers_java() {

		Integer maxElement = Collections.max(CENTERS_ROOKIE_YEAR);

		assertEquals(new Integer(1988), maxElement);
	}

	@Test
	public void find_max_value_from_list_of_integers_java8() {

		OptionalInt maxElement = CENTERS_ROOKIE_YEAR.stream().mapToInt(p -> p)
				.max();

		assertEquals(1988, maxElement.getAsInt());

		// or

		Optional<Integer> maxElement2 = CENTERS_ROOKIE_YEAR.stream().reduce(
				Integer::max);

		assertEquals(new Integer(1988), maxElement2.get());
	}

	@Test
	public void find_max_value_from_list_of_integers_guava_ordering() {

		Ordering<Integer> byYear = new Ordering<Integer>() {
			@Override
			public int compare(Integer left, Integer right) {
				return Ints.compare(left, right);
			}
		};

		assertEquals(new Integer(1988), byYear.max(CENTERS_ROOKIE_YEAR));
	}

	@Test
	public void find_max_value_from_list_of_integers_guava_ordering_shorthand() {

		Integer maxElement = Ordering.natural().max(CENTERS_ROOKIE_YEAR);

		assertEquals(new Integer(1988), maxElement);
	}

	@Test
	public void find_max_value_from_list_of_integers_apache() {

		Integer maxElement = ObjectUtils.max(CENTERS_ROOKIE_YEAR
				.toArray(new Integer[CENTERS_ROOKIE_YEAR.size()]));

		assertEquals(new Integer(1988), maxElement);
	}

}