Iterate over a HashMap Java using Lambda

In this post, I show you different ways to iterate over a HashMap in Java 8 lambda with an example.

• Iterating over a HashMap using Java 8 forEach and lambda.
• Iterating over the HashMap's entrySet using Java 8 forEach and lambda.
• Iterating over the HashMap's keySet.

Iterate over HashMap in Java 8

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class IterateOverHashMap {
    public static void main(String[] args) {
        Map<String, Double> employeeSalary = new HashMap<>();
        employeeSalary.put("David", 76000.00);
        employeeSalary.put("John", 120000.00);
        employeeSalary.put("Mark", 95000.00);
        employeeSalary.put("Steven", 134000.00);

        System.out.println("=== Iterating over a HashMap using Java 8 forEach and lambda ===");
        employeeSalary.forEach((employee, salary) -> {
            System.out.println(employee + " => " + salary);
        });
        System.out.println("\n=== Iterating over the HashMap's entrySet using Java 8 forEach and lambda ===");
        employeeSalary.entrySet().forEach(entry -> {
            System.out.println(entry.getKey() + " => " + entry.getValue());
        });

        System.out.println("\n=== Iterating over the HashMap's keySet ===");
        employeeSalary.keySet().forEach(employee -> {
            System.out.println(employee + " => " + employeeSalary.get(employee));
        });
    }
}

Output

=== Iterating over a HashMap using Java 8 forEach and lambda ===
David => 76000.0
John => 120000.0
Mark => 95000.0
Steven => 134000.0

=== Iterating over the HashMap's entrySet using Java 8 forEach and lambda ===
David => 76000.0
John => 120000.0
Mark => 95000.0
Steven => 134000.0

=== Iterating over the HashMap's keySet ===
David => 76000.0
John => 120000.0
Mark => 95000.0
Steven => 134000.0

Collections Examples

• Java LinkedHashMap Example
  
• Java HashSet Example
  
• Java LinkedList Example
  
• Java ArrayList Example
• Java Comparator Interface Example
• Java Comparable Interface Example
• Java IdentityHashMap Example
• Java WeakHashMap Example
• Java EnumMap Example
• Java CopyOnWriteArraySet Example
• Java EnumSet Class Example
• Guide to Java 8 forEach Method
• Different Ways to Iterate over a List in Java [Snippet]
• Different Ways to Iterate over a Set in Java [Snippet]
• Different Ways to Iterate over a Map in Java [Snippet]
• Iterate over TreeSet in Java Example
• Iterate over LinkedHashSet in Java Example
• Remove First and Last Elements of LinkedList in Java
• Iterate over LinkedList using an Iterator in Java
• Search an Element in an ArrayList in Java
• Iterate over ArrayList using Iterator in Java
• Remove Element from HashSet in Java
• Iterating over a HashSet using Iterator
• How To Remove Duplicate Elements From ArrayList In Java?
  
• Different Ways to Iterate over List, Set, and Map in Java

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