CombineTwoArrays.java

package com.levelup.java.array;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import java.util.Arrays;
import java.util.stream.Stream;

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

import com.google.common.collect.ObjectArrays;
import com.google.common.primitives.Ints;

/**
 * This java example will demonstrate combining or joining two arrays.
 * 
 * @author Justin Musgrove
 * @see <a
 *      href='http://www.leveluplunch.com/java/examples/join-two-arrays/'>Join
 *      two arrays</a>
 * 
 */
public class CombineTwoArrays {

	String[] firstHalfStateCapital = { "Montgomery", "Juneau", "Phoenix",
			"Little Rock", "Sacramento", "Denver", "Hartford", "Dover",
			"Tallahassee", "Atlanta", "Honolulu", "Boise", "Springfield",
			"Indianapolis", "Des Moines", "Topeka", "Frankfort", "Baton Rouge",
			"Augusta", "Annapolis", "Boston", "Lansing", "Saint Paul",
			"Jackson", "Jefferson City" };

	String[] secondHalfStateCapital = { "Helena", "Lincoln", "Carson City",
			"Concord", "Trenton", "Santa Fe", "Albany", "Raleigh", "Bismarck",
			"Columbus", "Oklahoma City", "Salem", "Harrisburg", "Providence",
			"Columbia", "Pierre", "Nashville", "Austin", "Salt Lake City",
			"Montpelier", "Richmond", "Olympia", "Charleston", "Madison",
			"Cheyenne" };

	int[] firstHalfStateCapitalByIndex = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
			12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 };

	int[] secondHalfStateCapitalByIndex = { 26, 27, 28, 29, 30, 31, 32, 33, 34,
			35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 };

	@Test
	public void join_two_object_arrays_in_java() {

		String[] allStateCapitals = new String[firstHalfStateCapital.length
				+ secondHalfStateCapital.length];

		// copy first half
		System.arraycopy(firstHalfStateCapital, 0, allStateCapitals, 0,
				firstHalfStateCapital.length);

		// copy second half
		System.arraycopy(secondHalfStateCapital, 0, allStateCapitals,
				firstHalfStateCapital.length, secondHalfStateCapital.length);

		assertTrue(allStateCapitals.length == 50);
	}

	@Test
	public void join_two_object_arrays_in_java8() {

		Stream<String> sa = Arrays.stream(firstHalfStateCapital);
		Stream<String> sb = Arrays.stream(secondHalfStateCapital);

		String[] allStateCapitals = Stream.concat(sa, sb).toArray(
				size -> new String[size]);

		assertTrue(allStateCapitals.length == 50);
	}

	@Test
	public void join_two_object_arrays_in_java_with_guava() {

		String[] allStateCapitals = ObjectArrays.concat(firstHalfStateCapital,
				secondHalfStateCapital, String.class);

		assertTrue(allStateCapitals.length == 50);
	}

	@Test
	public void join_two_primitive_arrays_in_java_with_guava() {

		int[] allStateCapitalsByIndex = Ints.concat(
				firstHalfStateCapitalByIndex, secondHalfStateCapitalByIndex);

		Arrays.toString(allStateCapitalsByIndex);
		assertEquals(50, allStateCapitalsByIndex.length);
	}

	@Test
	public void join_two_object_arrays_in_java_with_apache_commons() {

		String[] allStateCapitals = ArrayUtils.addAll(firstHalfStateCapital,
				secondHalfStateCapital);

		assertEquals(50, allStateCapitals.length);
	}

	@Test
	public void join_two_primitive_arrays_in_java_with_apache_commons() {

		int[] allStateCapitalsByIndex = ArrayUtils.addAll(
				firstHalfStateCapitalByIndex, secondHalfStateCapitalByIndex);

		assertEquals(50, allStateCapitalsByIndex.length);

	}

}