Iterate over a HashMap in Java - Four different ways

October 03, 2021

In this section, we will show you 4 different ways to iterate through a HashMap in Java.

Using Advanced for loop
Iterating over keys or values using keySet() and values() methods
Using Iterator
Using Java 8 forEach

1. Using Advanced for loop

// create hashmap
Map<Integer, String> lanuages = new HashMap<>();

// add 5 different key/values to map
lanuages.put(1, "Java");
lanuages.put(2, "Scala");
lanuages.put(3, "Kotlin");
lanuages.put(4, "Go");
lanuages.put(5, "Python");

// iterate via Advanced for loop
System.out.println("\n==> Advance For Loop Example..");
for (Map.Entry<Integer, String> entry : lanuages.entrySet()) {
    System.out.println(entry);
}

2. Iterating over keys or values using keySet() and values() methods

// create hashmap
Map<Integer, String> lanuages = new HashMap<>();

// add 5 different key/values to map
lanuages.put(1, "Java");
lanuages.put(2, "Scala");
lanuages.put(3, "Kotlin");
lanuages.put(4, "Go");
lanuages.put(5, "Python");

// Iterating over keys or values using keySet() and values() methods
System.out.println("\n==> Iterating over keys or values using keySet() and values() methods...");

// using keySet() for iteration over keys
for (Integer key : lanuages.keySet())
    System.out.println(key);

// using values() for iteration over keys
for (String value : lanuages.values())
    System.out.println(value);

3. Using Iterator

// create hashmap
Map<Integer, String> lanuages = new HashMap<>();

// add 5 different key/values to map
lanuages.put(1, "Java");
lanuages.put(2, "Scala");
lanuages.put(3, "Kotlin");
lanuages.put(4, "Go");
lanuages.put(5, "Python");

// iterate via "iterator loop"
System.out.println("\n==> Iterator Example...");
Iterator<Map.Entry<Integer, String>> it = lanuages.entrySet().iterator();
while (it.hasNext()) {
    Map.Entry<Integer, String> pair = (Map.Entry<Integer, String>) it.next();
    System.out.println(pair.getKey() + " = " + pair.getValue());
}

4. Using Java 8 forEach

// create hashmap
Map<Integer, String> lanuages = new HashMap<>();

// add 5 different key/values to map
lanuages.put(1, "Java");
lanuages.put(2, "Scala");
lanuages.put(3, "Kotlin");
lanuages.put(4, "Go");
lanuages.put(5, "Python");

// iterate via "iterator loop"
System.out.println("\n==> Iterator Example...");
Iterator<Map.Entry<Integer, String>> it = lanuages.entrySet().iterator();
while (it.hasNext()) {
    Map.Entry<Integer, String> pair = (Map.Entry<Integer, String>) it.next();
    System.out.println(pair.getKey() + " = " + pair.getValue());
}