Java LinkedHashMap forEach() Method

The LinkedHashMap.forEach(BiConsumer<? super K, ? super V> action) method in Java is used to perform the given action for each entry in the LinkedHashMap.

Table of Contents

1. Introduction
2. forEach Method Syntax
3. Examples
   • Iterating Over Entries in a LinkedHashMap
   • Modifying Entries Using forEach
4. Real-World Use Case
   • Example: Displaying User Information
5. Conclusion

Introduction

The LinkedHashMap.forEach(BiConsumer<? super K, ? super V> action) method is a member of the LinkedHashMap class in Java. It allows you to perform a specified action for each entry in the map. The action is specified as a BiConsumer that takes two arguments: the key and the value. This method is useful for applying operations to all entries in the map.

forEach() Method Syntax

The syntax for the forEach method is as follows:

public void forEach(BiConsumer<? super K, ? super V> action)

• The method takes one parameter:
  • action of type BiConsumer<? super K, ? super V>, which represents the action to be performed for each entry.
• The method does not return a value.

Examples

Iterating Over Entries in a LinkedHashMap

The forEach method can be used to iterate over the entries in a LinkedHashMap.

Example

import java.util.LinkedHashMap;
import java.util.function.BiConsumer;

public class ForEachExample {
    public static void main(String[] args) {
        // Creating a LinkedHashMap with String keys and Integer values
        LinkedHashMap<String, Integer> people = new LinkedHashMap<>();

        // Adding entries to the LinkedHashMap
        people.put("Ravi", 25);
        people.put("Priya", 30);
        people.put("Vijay", 35);

        // Using forEach to iterate over the entries
        people.forEach(new BiConsumer<String, Integer>() {
            @Override
            public void accept(String key, Integer value) {
                System.out.println(key + ": " + value);
            }
        });
    }
}

Output:

Ravi: 25
Priya: 30
Vijay: 35

Using Lambda Expression with forEach

You can also use a lambda expression to simplify the code.

Example

import java.util.LinkedHashMap;

public class ForEachLambdaExample {
    public static void main(String[] args) {
        // Creating a LinkedHashMap with String keys and Integer values
        LinkedHashMap<String, Integer> people = new LinkedHashMap<>();

        // Adding entries to the LinkedHashMap
        people.put("Ravi", 25);
        people.put("Priya", 30);
        people.put("Vijay", 35);

        // Using forEach with a lambda expression to iterate over the entries
        people.forEach((key, value) -> System.out.println(key + ": " + value));
    }
}

Output:

Ravi: 25
Priya: 30
Vijay: 35

Modifying Entries Using forEach

You can also modify the values in the LinkedHashMap using the forEach method.

Example

import java.util.LinkedHashMap;

public class ModifyValuesExample {
    public static void main(String[] args) {
        // Creating a LinkedHashMap with String keys and Integer values
        LinkedHashMap<String, Integer> people = new LinkedHashMap<>();

        // Adding entries to the LinkedHashMap
        people.put("Ravi", 25);
        people.put("Priya", 30);
        people.put("Vijay", 35);

        // Using forEach to modify the values
        people.forEach((key, value) -> {
            if (key.equals("Priya")) {
                people.put(key, value + 1);
            }
        });

        // Printing the modified LinkedHashMap
        System.out.println("Modified LinkedHashMap: " + people);
    }
}

Output:

Modified LinkedHashMap: {Ravi=25, Priya=31, Vijay=35}

Real-World Use Case

Example: Displaying User Information

A common real-world use case for LinkedHashMap.forEach(BiConsumer<? super K, ? super V> action) is displaying user information stored in a LinkedHashMap. For example, let's consider a scenario where user profiles are stored with usernames as keys and ages as values.

Example

import java.util.LinkedHashMap;

public class DisplayUserInformation {
    public static void main(String[] args) {
        // Creating a LinkedHashMap to store user profiles
        LinkedHashMap<String, Integer> userProfiles = new LinkedHashMap<>();

        // Adding user profiles to the LinkedHashMap
        userProfiles.put("Ravi", 25);
        userProfiles.put("Priya", 30);
        userProfiles.put("Vijay", 35);

        // Using forEach to display user information
        System.out.println("User Information:");
        userProfiles.forEach((username, age) -> System.out.println("Username: " + username + ", Age: " + age));
    }
}

Output:

User Information:
Username: Ravi, Age: 25
Username: Priya, Age: 30
Username: Vijay, Age: 35

In this example, LinkedHashMap.forEach(BiConsumer<? super K, ? super V> action) is used to display user information stored in a LinkedHashMap, demonstrating how to iterate over and access entries in the map.

Conclusion

The LinkedHashMap.forEach() method in Java provides a way to perform a specified action for each entry in the LinkedHashMap. By understanding how to use this method, you can efficiently manage and manipulate collections of key-value pairs in your Java applications. The method allows you to iterate over entries, modify values, and perform operations based on the entries, making it a versatile tool for data management.