HashMap extends AbstractMap and is similar to Hashtable. : Map « Utility Classes « SCJP

1. SCJP
2. Utility Classes
3. Map

A Map combines two collections, called keys and values. 


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

public class MainClass {
  public static void main(String[] argv) {
    Map map = new HashMap();
    map.put("key", "value");

    System.out.println(map);
  }
}

{key=value}