Simple example of using an apache commons MultiValueMap to store and retrieve entries with multiple values

Multivaluemap.java

package Multivaluemap1.multivaluemap;

import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;

import org.apache.commons.collections4.map.MultiValueMap;

/**
 * example of using an apache commons MultiValueMap to store and retrieve
 * entries with multiple values per entry
 * 
 * this should produce the following output

  key:key1, values=[value1, value2]
     value:value1
     value:value2
  key:key2, values=[value3]
     value:value3

 
 * this is dependent on the following:
  		<dependency>
			<groupId>org.apache.commons</groupId>
			<artifactId>commons-collections4</artifactId>
			<version>4.0</version>
		</dependency>
 */


public class Multivaluemap {

	public static void main(String[] args) {

		@SuppressWarnings("unchecked")
		MultiValueMap<String, String> orderedMap = 
		           MultiValueMap.multiValueMap(
		                new LinkedHashMap<String, Collection<String>>(), 
		                (Class<LinkedHashSet<String>>)(Class<?>)LinkedHashSet.class
		           );
		
		orderedMap.put("key1", "value1");
		orderedMap.put("key1", "value2");
		
		orderedMap.put("key2", "value3");
		
		Iterator<String> mapIterator = orderedMap.keySet().iterator();
		
		// iterate over the map
		while (mapIterator.hasNext()) {
			String key = mapIterator.next();
			System.out.println("key:" + key + ", values=" + orderedMap.get(key));
			
			Collection<String> values = orderedMap.getCollection(key);
			
			// iterate over the entries for this key in the map
			for(Iterator<String> entryIterator = values.iterator(); entryIterator.hasNext();) {
				String value = entryIterator.next();
				
				System.out.println("    value:" + value);
			}
		
		}

	}

}