why use hashmaps in java code example

Example 1: hashmaps java

import java.util.HashMap;
//Within a class
//You can do new HashMap<Key Type, Value Type>();, but you don't need to
HashMap<Int, String> examplehashmap=new HashMap<>();
{
//put in values
 examplehashmap.put(5, "example");
};
//get value
examplehashmap.get(5);
//returns "example"

Example 2: java hashmap example

//Hash map creation
Map< String,Integer> hm =  
                        new HashMap< String,Integer>(); 
//inserting elements into hashmap
       hm.put("a", new Integer(100)); 
       hm.put("b", new Integer(200)); 
       hm.put("c", new Integer(300)); 
       hm.put("d", new Integer(400));