The Map collection

We have one more collection, called Map. We will take an example and discuss Map as we proceed with the code. This interface takes the values in the form of a key and value pair. 

We create a class, hashMapexample, and within that the we define HashMap. HashMap requires two types of argument, such as Integer and String:

package coreJava;

import java.util.HashMap;

public class hashMapexample {

    public static void main(String[] args) {

       HashMap<Integer, String> hm= new HashSet<Integer, String>();

    }
}

Here, Integer is the key and String is the value. Now if you type hm. in your IDE, you will see a few methods present in HashMap; let's use the put method:

        hm.put(0, "hello");
        hm.put(1, "goodbye");
        hm.put(2, "morning");
        hm.put(3, "evening");

The put method takes the input in the form of keys and values. Also, the value of the key needs to be an integer, it can be a string as well. The key is just something we define for...