Double-Curly

import java.util.HashMap;
import java.util.Map;

public class Test
{
    public static void main(String[] args)
    {
        Map<String, String> m = new HashMap<String, String>(){{
            this.put("foo", "1");
            this.put("bar", "2");
        }};

        //prints "class Test$1" or similar
        System.out.println(m.getClass());
        // prints true
        System.out.println(m instanceof Map);
        // prints true
        System.out.println(m instanceof HashMap);
        // prints false
        System.out.println(m.getClass().equals(HashMap.class));
        // prints true
        System.out.println(HashMap.class.isAssignableFrom(m.getClass()));
    }
}