HashMap in Java

Map in Java has Key-Value pairs

To access the value you must know the Key in the HashMap. Hashmap uses a technique of Hashing

HashMap does not allow duplicates for the Keys.

Below is the simple HashMap program in Java to demonstrate the Key-Value objects in HashMap

HashExMain.java:

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

public class HashExMain {

    public static void main (String [] args){

        HashMap<Integer, EmployeeDetails> map = new HashMap<Integer, EmployeeDetails>();

        EmployeeDetails empOne = new EmployeeDetails(101, "Andrew Heins");

        EmployeeDetails empTwo = new EmployeeDetails(102, "Bill patrick");

        map.put(1, empOne);

        map.put(2, empTwo);

        for (HashMap.Entry<Integer, EmployeeDetails> entry : map.entrySet())

        {

            EmployeeDetails e = entry.getValue();

            System.out.println("The Key is "  + entry.getKey() + " " + "& " + "The value is " + e.emplNo + " &" + " " + e.emplName);

        }

    }

}

EmployeeDetails.java:

public class EmployeeDetails {

    int emplNo;

    String emplName;

    public EmployeeDetails(int emplNo, String emplName){

        this.emplNo = emplNo;

        this.emplName = emplName;

    }

}

Getting ConcurrentModificationException ? Check out how to avoid this exception in the blog post 

ConcurrentHashMap