HashMap is an object that stores both “key/value” as a pairs. In this article, we show you how to create a HashMap instance and iterates the HashMap data.

["mkyong","1000.00"] = ["key","value"]

In above, “mkyong” is the key , “1000.00” is the value. By given a key “mkyong”, you can get the value “1000.00”.


See full example of using HashMap.

package com.mkyong.core;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class Number {
	public static void main(String[] args) {
		try {

			Map mMap = new HashMap();
			mMap.put("PostgreSQL", "Free Open Source Enterprise Database");
			mMap.put("DB2", "Enterprise Database , It's expensive");
			mMap.put("Oracle", "Enterprise Database , It's expensive");
			mMap.put("MySQL", "Free Open SourceDatabase");

			Iterator iter = mMap.entrySet().iterator();

			while (iter.hasNext()) {
				Map.Entry mEntry = (Map.Entry) iter.next();
				System.out.println(mEntry.getKey() + " : " + mEntry.getValue());

			mMap.put("Oracle", "Enterprise Database , It's free now ! (hope)");

			System.out.println("One day Oracle.. : " + mMap.get("Oracle"));

		} catch (Exception e) {


PostgreSQL : Free Open Source Enterprise Database
MySQL : Free Open SourceDatabase
Oracle : Enterprise Database , It's expensive
DB2 : Enterprise Database , It's expensive
One day Oracle.. : Enterprise Database , It's free now ! (hope)