JoinerExample.java

package com.levelup.java.guava;

import static org.junit.Assert.assertEquals;

import java.util.List;

import org.junit.Test;

import com.google.common.base.Joiner;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Multimap;

/**
 * This java example will demonstrate examples of 
 * Google Guava Joiner
 * 
 * @author Justin Musgrove
 * @see <a href='http://www.leveluplunch.com/java/examples/guava-joiner-example/'>Joiner example</a>
 * 
 */
public class JoinerExample {

	
	@Test
	public void join_a_list_of_strings () { 

		List<String> cloudGroups = Lists.newArrayList(
				"Cirrus", "Alto", "Stratus", 
				"Vertical Growth", "Special Clouds");  
		
		String cloudGroupsJoined = Joiner.on(",").join(cloudGroups);
		
		assertEquals("Cirrus,Alto,Stratus,Vertical Growth,Special Clouds", 
				cloudGroupsJoined);
	}
	
	@Test
	public void join_a_list_of_strings_skipping_null () {
		
		List<String> cloudGroups = Lists.newArrayList(
				"Cirrus", "Alto", null, null, 
				"Stratus", "Vertical Growth", "Special Clouds", null);  

		String cloudGroupsJoined = Joiner.on(",").skipNulls().join(cloudGroups);
		
		assertEquals("Cirrus,Alto,Stratus,"
				+ "Vertical Growth,Special Clouds", 
				cloudGroupsJoined);
	}

	/**
	 * Join a list of strings, add 'and' between each element, 
	 * replace null with '[unknown]'
	 */
	@Test
	public void join_a_list_of_strings_replacing_null () {
		
		List<String> cloudGroups = Lists.newArrayList(
				"Cirrus", "Alto", null, null, 
				"Stratus", "Vertical Growth", "Special Clouds", null);
		
		String cloudGroupsJoined = Joiner
				.on(" and ")
				.useForNull("[unknown]")
				.join(cloudGroups);

		assertEquals("Cirrus and Alto and [unknown] and [unknown] "
				+ "and Stratus and Vertical Growth "
				+ "and Special Clouds and [unknown]", 
				cloudGroupsJoined);
	}
	
	@Test
	public void join_key_values_map () {
		Multimap<String, String> clouds = ArrayListMultimap.create();
		
		clouds.put("Cirrus", "Cirrus");
		clouds.put("Cirrus", "Cirrostratus");
		clouds.put("Cirrus", "Cirrocumulus");
		
		clouds.put("Alto", "Altostratus");
		clouds.put("Alto", "Altocumulus");
		
		clouds.put("Stratus", "Stratus");
		clouds.put("Stratus", "Stratocumulus");
		clouds.put("Stratus", "Nimbostratus");
		
		clouds.put("Vertical Growth", "Cumulus");
		clouds.put("Vertical Growth", "Cumulonimbus");
		
		clouds.put("Special Clouds", "Mammatus");
		clouds.put("Special Clouds", "Lenticular");
		clouds.put("Special Clouds", "Fog");
		clouds.put("Special Clouds", "Contrails");
		
		String keysAndValuesJoined = Joiner
				.on(", ")
				.withKeyValueSeparator(" has type ")
				.join(clouds.entries());
		
		assertEquals("Cirrus has type Cirrus, "
				+ "Cirrus has type Cirrostratus, "
				+ "Cirrus has type Cirrocumulus, "
				+ "Vertical Growth has type Cumulus, "
				+ "Vertical Growth has type Cumulonimbus, "
				+ "Alto has type Altostratus, "
				+ "Alto has type Altocumulus, "
				+ "Stratus has type Stratus, "
				+ "Stratus has type Stratocumulus, "
				+ "Stratus has type Nimbostratus, "
				+ "Special Clouds has type Mammatus, "
				+ "Special Clouds has type Lenticular, "
				+ "Special Clouds has type Fog, "
				+ "Special Clouds has type Contrails", 
				keysAndValuesJoined);
	}
	
}