Creating a HashMap with entries

Problem: Create an instance of HashMap in Java with entries in it. I don't want to create a new HashMap instance and keep adding entries to it. I want to have a concise way of creating a HashMap with entries.

Solution: Guava library comes with factory methods that can create a HashMap without using the verbose form of "Map myMap = new HashMap()". You can simply say "Map myMap = newHashMap()", assuming you have done a static import of the Maps.newHashMap method. But that is not sufficient. It would be better to provide a utility method that looks like this: "Map myMap = newHashMapWithEntries(firstKey, firstValue, secondKey, secondValue)". That way it is easy to create static-final maps instead of writing a separate method to populate them or to populate them from constructor, as given below:

public class MyClass { 
   private static final Map<String, URL> serviceUrls = createServiceUrlsMap(); 
   private static Map<String, String> createServiceUrlsMap() { 
    Map<String, URL> retVal = new HashMap<String, URL>(); 
    retVal.put("google", new URL("http://www.google.com"); 
    retVal.put("yahoo", new URL("http://www.yahoo.com"); 
    return retVal; 
   } 
 } 

That is too verbose. What I want is something like:

public class MyClass { 
   private static final Map<String, URL> serviceUrls = newHashMapWithEntries( 
       "google", new URL("http://www.google.com"), 
       "yahoo", new URL("http://www.yahoo.com"));  
 }

So here is one possible implementation of newHashMapWithEntries:

    @SuppressWarnings("unchecked")
    public static <K, V> Map<K, V> newHashMapWithEntries(K firstKey, V firstValue, Object... rest) {
        if(rest.length%2 != 0) {
            throw new IllegalArgumentException("Expected the number of args to be even.");
        }
       
        Class<? extends Object> keyType = firstKey.getClass();
        Class<? extends Object> valueType = firstValue.getClass();
        Map<K, V> retVal = new HashMap<K, V>();
        retVal.put(firstKey, firstValue);
        for(int i = 0; i < rest.length; i += 2) {
            if(!keyType.isAssignableFrom(rest[i].getClass())) {
                throw new IllegalArgumentException("Expected all keys to be of type <? extends " +
                        keyType.getName() + ">, but found " + rest[i].getClass().getName() + ".");
            }
            if(!valueType.isAssignableFrom(rest[i+1].getClass())) {
                throw new IllegalArgumentException("Expected all values to be of type <? extends " +
                        valueType.getName() + ">, but found " + rest[i+1].getClass().getName() + ".");
            }
            retVal.put((K)rest[i], (V)rest[i+1]);
        }
        return retVal;
    }