Java Program to Iterate over a HashMap

In this article, we will understand how to iterate over a HashMap. Java HashMap is a hash table based implementation of Java's Map interface. It is a collection of key-value pairs.

Below is a demonstration of the same −

Suppose our input is −

Input Hashmap: {Java=Enterprise, JavaScript=Frontend, Mysql=Backend, Python=ML/AI}

The desired output would be −

The keys of the Hashmap are: Java, JavaScript, Mysql, Python, The Values of the Hashmap are: Enterprise, Frontend, Backend, ML/AI,

Algorithm

Step 1 - START Step 2 - Declare namely Step 3 - Define the values. Step 4 - Create a hashmap of strings and initialize elements in it using the ‘put’ method. Step 5 - Display the hashmap on the console. Step 6 - Iterate over the elements of the hashmap, and fetch each key using ‘keySet’ method. Step 7 - Display this on the console. Step 6 - Stop

Example 1

Here, we bind all the operations together under the ‘main’ function.

import java.util.HashMap; import java.util.Map.Entry; public class Demo {    public static void main(String[] args) {       System.out.println("The required packages have been imported");       HashMap<String, String> input_map = new HashMap<>();       input_map.put("Java", "Enterprise");       input_map.put("Python", "ML/AI");       input_map.put("JavaScript", "Frontend");       input_map.put("Mysql", "Backend");       System.out.println("The HashMap is defined as: " + input_map);       System.out.print("\nThe keys of the Hashmap are: ");       for(String key: input_map.keySet()) {          System.out.print(key);          System.out.print(", ");       }       System.out.print("\nThe Values of the Hashmap are: ");       for(String value: input_map.values()) {          System.out.print(value);          System.out.print(", ");       }    } }

Output

The required packages have been imported The HashMap is defined as: {Java=Enterprise, JavaScript=Frontend, Mysql=Backend, Python=ML/AI} The keys of the Hashmap are: Java, JavaScript, Mysql, Python, The Values of the Hashmap are: Enterprise, Frontend, Backend, ML/AI,

Example 2

Here, we encapsulate the operations into functions exhibiting object oriented programming.

import java.util.HashMap; public class Demo {    static void print_keys(HashMap<String, String> input_map){       System.out.print("\nThe keys of the Hashmap are: ");       for(String key: input_map.keySet()) {          System.out.print(key);          System.out.print(", ");       }    }    static void print_values( HashMap<String, String> input_map){       System.out.print("\nThe Values of the Hashmap are: ");       for(String value: input_map.values()) {          System.out.print(value);          System.out.print(", ");       }    }    public static void main(String[] args) {       System.out.println("The required packages have been imported");       HashMap<String, String> input_map = new HashMap<>();       input_map.put("Java", "Enterprise");       input_map.put("Python", "ML/AI");       input_map.put("JavaScript", "Frontend");       input_map.put("Mysql", "Backend");       System.out.println("The HashMap is defined as: " + input_map);       print_keys(input_map);       print_values(input_map);    } }

Output

The required packages have been imported The HashMap is defined as: {Java=Enterprise, JavaScript=Frontend, Mysql=Backend, Python=ML/AI} The keys of the Hashmap are: Java, JavaScript, Mysql, Python, The Values of the Hashmap are: Enterprise, Frontend, Backend, ML/AI,