Iterate over HashMap in Java

In this post, I show you different ways to iterate over a HashMap in Java with an example.
  • Iterating over a HashMap using Java 8 forEach and lambda.
  • Iterating over the HashMap's entrySet using iterator().
  • Iterating over the HashMap's entrySet using Java 8 forEach and lambda.
  • Iterating over the HashMap's entrySet using a simple for-each loop.
  • Iterating over the HashMap's keySet.

Iterate over HashMap in Java

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 iterator() ===");
        Set<Map.Entry<String, Double>> employeeSalaryEntries = employeeSalary.entrySet();
        Iterator<Map.Entry<String, Double>> employeeSalaryIterator = employeeSalaryEntries.iterator();
        while (employeeSalaryIterator.hasNext()) {
            Map.Entry<String, Double> entry = employeeSalaryIterator.next();
            System.out.println(entry.getKey() + " => " + entry.getValue());
        }

        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 entrySet using simple for-each loop ===");
        for(Map.Entry<String, Double> entry: employeeSalary.entrySet()) {
            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 iterator() ===
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 entrySet using simple for-each loop ===
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


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