Simple Java HashMap example
- /*
- Simple Java HashMap example
- This simple Java Example shows how to use Java HashMap. It also describes how to
- add something to HashMap and how to retrieve the value added from HashMap.
- */
- import java.util.HashMap;
- public class JavaHashMapExample {
- public static void main(String[] args) {
- //create object of HashMap
- HashMap hMap = new HashMap();
- /*
- Add key value pair to HashMap using
- Object put(Object key, Object value) method of Java HashMap class,
- where key and value both are objects
- put method returns Object which is either the value previously tied
- to the key or null if no value mapped to the key.
- */
- hMap.put("One", new Integer(1));
- hMap.put("Two", new Integer(2));
- /*
- Please note that put method accepts Objects. Java Primitive values CAN NOT
- be added directly to HashMap. It must be converted to corrosponding
- wrapper class first.
- */
- //retrieve value using Object get(Object key) method of Java HashMap class
- Object obj = hMap.get("One");
- System.out.println(obj);
- /*
- Please note that the return type of get method is an Object. The value must
- be casted to the original class.
- */
- }
- }
- /*
- Output of the program would be
- 1
- */
