Map<String, String> map = ...
for (Map.Entry<String, String> entry : map.entrySet()) {
System.out.println(entry.getKey() + "/" + entry.getValue());
}
On Java 10+:
for (var entry : map.entrySet()) {
System.out.println(entry.getKey() + "/" + entry.getValue());
}
Baeldung
baeldung.com › home › java › java collections › java map › iterate over a map in java
Iterate Over a Map in Java | Baeldung
December 16, 2024 - In the code above, we invoke forEachKeyValue() on a MutableMap object to iterate through the Map and use a lambda expression to get the keys and values.
Top answer 1 of 16
5965
Map<String, String> map = ...
for (Map.Entry<String, String> entry : map.entrySet()) {
System.out.println(entry.getKey() + "/" + entry.getValue());
}
On Java 10+:
for (var entry : map.entrySet()) {
System.out.println(entry.getKey() + "/" + entry.getValue());
}
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To summarize the other answers and combine them with what I know, I found 10 main ways to do this (see below). Also, I wrote some performance tests (see results below). For example, if we want to find the sum of all of the keys and values of a map, we can write:
Using iterator and Map.Entry
long i = 0; Iterator<Map.Entry<Integer, Integer>> it = map.entrySet().iterator(); while (it.hasNext()) { Map.Entry<Integer, Integer> pair = it.next(); i += pair.getKey() + pair.getValue(); }Using foreach and Map.Entry
long i = 0; for (Map.Entry<Integer, Integer> pair : map.entrySet()) { i += pair.getKey() + pair.getValue(); }Using forEach from Java 8
final long[] i = {0}; map.forEach((k, v) -> i[0] += k + v);Using keySet and foreach
long i = 0; for (Integer key : map.keySet()) { i += key + map.get(key); }Using keySet and iterator
long i = 0; Iterator<Integer> itr2 = map.keySet().iterator(); while (itr2.hasNext()) { Integer key = itr2.next(); i += key + map.get(key); }Using for and Map.Entry
long i = 0; for (Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator(); entries.hasNext(); ) { Map.Entry<Integer, Integer> entry = entries.next(); i += entry.getKey() + entry.getValue(); }Using the Java 8 Stream API
final long[] i = {0}; map.entrySet().stream().forEach(e -> i[0] += e.getKey() + e.getValue());Using the Java 8 Stream API parallel
final long[] i = {0}; map.entrySet().stream().parallel().forEach(e -> i[0] += e.getKey() + e.getValue());Using IterableMap of
Apache Collectionslong i = 0; MapIterator<Integer, Integer> it = iterableMap.mapIterator(); while (it.hasNext()) { i += it.next() + it.getValue(); }Using MutableMap of Eclipse (CS) collections
final long[] i = {0}; mutableMap.forEachKeyValue((key, value) -> { i[0] += key + value; });
Perfomance tests (mode = AverageTime, system = Windows 8.1 64-bit, Intel i7-4790 3.60 GHz, 16 GB)
For a small map (100 elements), score 0.308 is the best
Benchmark Mode Cnt Score Error Units test3_UsingForEachAndJava8 avgt 10 0.308 ± 0.021 µs/op test10_UsingEclipseMap avgt 10 0.309 ± 0.009 µs/op test1_UsingWhileAndMapEntry avgt 10 0.380 ± 0.014 µs/op test6_UsingForAndIterator avgt 10 0.387 ± 0.016 µs/op test2_UsingForEachAndMapEntry avgt 10 0.391 ± 0.023 µs/op test7_UsingJava8StreamApi avgt 10 0.510 ± 0.014 µs/op test9_UsingApacheIterableMap avgt 10 0.524 ± 0.008 µs/op test4_UsingKeySetAndForEach avgt 10 0.816 ± 0.026 µs/op test5_UsingKeySetAndIterator avgt 10 0.863 ± 0.025 µs/op test8_UsingJava8StreamApiParallel avgt 10 5.552 ± 0.185 µs/opFor a map with 10000 elements, score 37.606 is the best
Benchmark Mode Cnt Score Error Units test10_UsingEclipseMap avgt 10 37.606 ± 0.790 µs/op test3_UsingForEachAndJava8 avgt 10 50.368 ± 0.887 µs/op test6_UsingForAndIterator avgt 10 50.332 ± 0.507 µs/op test2_UsingForEachAndMapEntry avgt 10 51.406 ± 1.032 µs/op test1_UsingWhileAndMapEntry avgt 10 52.538 ± 2.431 µs/op test7_UsingJava8StreamApi avgt 10 54.464 ± 0.712 µs/op test4_UsingKeySetAndForEach avgt 10 79.016 ± 25.345 µs/op test5_UsingKeySetAndIterator avgt 10 91.105 ± 10.220 µs/op test8_UsingJava8StreamApiParallel avgt 10 112.511 ± 0.365 µs/op test9_UsingApacheIterableMap avgt 10 125.714 ± 1.935 µs/opFor a map with 100000 elements, score 1184.767 is the best
Benchmark Mode Cnt Score Error Units test1_UsingWhileAndMapEntry avgt 10 1184.767 ± 332.968 µs/op test10_UsingEclipseMap avgt 10 1191.735 ± 304.273 µs/op test2_UsingForEachAndMapEntry avgt 10 1205.815 ± 366.043 µs/op test6_UsingForAndIterator avgt 10 1206.873 ± 367.272 µs/op test8_UsingJava8StreamApiParallel avgt 10 1485.895 ± 233.143 µs/op test5_UsingKeySetAndIterator avgt 10 1540.281 ± 357.497 µs/op test4_UsingKeySetAndForEach avgt 10 1593.342 ± 294.417 µs/op test3_UsingForEachAndJava8 avgt 10 1666.296 ± 126.443 µs/op test7_UsingJava8StreamApi avgt 10 1706.676 ± 436.867 µs/op test9_UsingApacheIterableMap avgt 10 3289.866 ± 1445.564 µs/op
Graphs (performance tests depending on map size)
Table (perfomance tests depending on map size)
100 600 1100 1600 2100
test10 0.333 1.631 2.752 5.937 8.024
test3 0.309 1.971 4.147 8.147 10.473
test6 0.372 2.190 4.470 8.322 10.531
test1 0.405 2.237 4.616 8.645 10.707
test2 0.376 2.267 4.809 8.403 10.910
test7 0.473 2.448 5.668 9.790 12.125
test9 0.565 2.830 5.952 13.220 16.965
test4 0.808 5.012 8.813 13.939 17.407
test5 0.810 5.104 8.533 14.064 17.422
test8 5.173 12.499 17.351 24.671 30.403
All tests are on GitHub.
java - Iterate through a HashMap - Stack Overflow
Since all maps in Java implement the Map interface, the following techniques will work for any map implementation (HashMap, TreeMap, LinkedHashMap, Hashtable, etc.) Method #1: Iterating over entries using a For-Each loop. This is the most common method and is preferable in most cases. It should be used if you need both map keys ... More on stackoverflow.com
loops - How to iterate through a Map in java? - Stack Overflow
Check out for more examples about iteration through maps in Java. More on stackoverflow.com
How do I efficiently iterate over each entry in a Java Map?
What are the best practices for iterating over key-value pairs in a Java Map? In this guide, we'll explore different ways to traverse a Map efficiently usi... More on janbasktraining.com
1
April 18, 2025Is the iteration order of HashSet deterministic?
If you iterate over a hashmap, and then iterate over it again, you will get the same order. If you clone into a different hashmap, you will get a different order, and if you rerun the program, you'll get yet another order. Additionally, inserting new elements and removing old elements also will change the iteration order arbitrarily. If all you do is immutable operations to one map in one invocation of the program, though, iteration order is stable. More on reddit.com
22
23
January 6, 202111:27
5 Best Ways to Iterate Over HashMap in Java
13:31
Iterating over a HashMap | Different Ways to Iterate over HashMap ...
11:27
5 Best Ways to Iterate Over HashMap in Java - YouTube
09:03
5 Ways to Iterate a Map in Java - Simple and Easy! - YouTube
13:34
Different Ways to Iterate Through a Map in Java - YouTube
GeeksforGeeks
geeksforgeeks.org › java › iterate-map-java
How to Iterate Any Map in Java? - GeeksforGeeks
September 1, 2026 - Java 8 introduced the forEach() method, which allows us to iterate over a map using a lambda expression. It provides a short and readable way to process key-value pairs.
Medium
medium.com › javarevisited › iterating-over-maps-is-an-important-topic-when-it-comes-to-working-with-maps-in-java-549deacdeaf9
Iterating over maps is an important topic when it comes to working with maps in Java.
October 10, 2023 - There are three main ways to iterate over a map in Java: Iterating over keys: In this method, we obtain the set of keys from the map using the keySet() method and iterate over the set using a for-each loop or an iterator.
Top answer 1 of 7
5421
If you're only interested in the keys, you can iterate through the keySet() of the map:
Map<String, Object> map = ...;
for (String key : map.keySet()) {
// ...
}
If you only need the values, use values():
for (Object value : map.values()) {
// ...
}
Finally, if you want both the key and value, use entrySet():
for (Map.Entry<String, Object> entry : map.entrySet()) {
String key = entry.getKey();
Object value = entry.getValue();
// ...
}
One caveat: if you want to remove items mid-iteration, you'll need to do so via an Iterator (see karim79's answer). However, changing item values is OK (see Map.Entry).
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3458
Iterate through the entrySet() like so:
public static void printMap(Map mp) {
Iterator it = mp.entrySet().iterator();
while (it.hasNext()) {
Map.Entry pair = (Map.Entry)it.next();
System.out.println(pair.getKey() + " = " + pair.getValue());
it.remove(); // avoids a ConcurrentModificationException
}
}
Read more about Map.
Techie Delight
techiedelight.com › home › java › iterate map in java using keyset() method
Iterate Map in Java using keySet() method | Techie Delight
July 7, 2026 - Since the map doesn’t extend the Collection interface, it doesn’t have its own iterator. Since Set extends the Collection interface, we can get an iterator to set of keys returned by keySet().
Squash
squash.io › how-to-iterate-over-entries-in-a-java-map
How To Iterate Over Entries In A Java Map - Squash Labs
November 24, 2023 - For each key, we retrieve the corresponding value using the get() method of the map. Finally, we print the key-value pair. The question of how to iterate over entries in a Java Map is commonly asked by Java developers who need to process or manipulate the data stored in a map.
ProsperaSoft
prosperasoft.com › home › blogs › full-stack › backend › java › iterate java map
How do I efficiently iterate over each entry in a Java Map? - ProsperaSoft blogs
May 29, 2025 - One of the most efficient ways to iterate over a Java Map is by utilizing the entrySet() method combined with a for-each loop. This method allows you to traverse both keys and values simultaneously.
Top answer 1 of 3
52
For basic utilisation, the HashMap is the best, I've put how to iterate over it, easier than using an iterator :
public static void main (String[] args) {
//a map with key type : String, value type : String
Map<String,String> mp = new HashMap<String,String>();
mp.put("John","Math"); mp.put("Jack","Math"); map.put("Jeff","History");
//3 differents ways to iterate over the map
for (String key : mp.keySet()){
//iterate over keys
System.out.println(key+" "+mp.get(key));
}
for (String value : mp.values()){
//iterate over values
System.out.println(value);
}
for (Entry<String,String> pair : mp.entrySet()){
//iterate over the pairs
System.out.println(pair.getKey()+" "+pair.getValue());
}
}
A quick explanation :
for (String name : mp.keySet()){
//Do Something
}
means : "For all string from the keys of the map, we'll do something, and at each iteration we will call the key 'name' (it can be whatever you want, it's a variable)
Here we go :
public String[] getAllKeys(){
int i = 0;
String allkeys[] = new String[buckets.length];
KeyValue val = buckets[i];
//Look at the first one
if(val != null) {
allkeys[i] = val.key;
i++;
}
//Iterate until there is no next
while(val.next != null){
allkeys[i] = val.next.key;
val = val.next;
i++;
}
return allkeys;
}
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3
See if this helps,
HashMap< String, String> map = new HashMap<>();
Set<String> keySet = map.keySet();
Iterator<String> iterator = keySet.iterator();
while(iterator.hasNext())
{
//iterate over keys
}
//or iterate over entryset
Iterator<Entry<String, String>> iterator2 = map.entrySet().iterator();
while(iterator2.hasNext())
{
Entry<String, String> next = iterator2.next();
//get key
next.getKey();
//get value
next.getValue();
}
DevQA
devqa.io › 4-different-ways-iterate-map-java
Different Ways to Iterate Through a Map in Java
Map<Integer, Integer> map = new HashMap<Integer, Integer>(); for (Integer key : map.keySet()) { System.out.println("Key = " + key); } for (Integer value : map.values()) { System.out.println("Value = " + value); } ... Map<Integer, Integer> map ...
LabEx
labex.io › tutorials › java-how-to-loop-through-java-map-keys-425177
How to loop through Java Map keys | LabEx
Map<String, Integer> data = new HashMap<>(); try { data.keySet().forEach(key -> { try { // Potential risky operation processKey(key, data.get(key)); } catch (Exception e) { // Handle individual key processing errors System.err.println("Error processing key: " + key); } }); } catch (Exception e) { // Global error handling System.err.println("Iteration failed"); } RUN · Use appropriate iteration method based on use case ... At LabEx, we emphasize understanding these practical techniques to write robust and efficient Java code. By exploring different methods of looping through Java Map keys, developers can select the most appropriate approach based on their specific programming requirements.
ConcretePage
concretepage.com › java › how-iterate-map-java
How to Iterate Map in Java
January 31, 2022 - Iterate over keys. for (Integer key : map.keySet()) { System.out.println(key + " " + map.get(key)); } Map.values
Programiz
programiz.com › java-programming › examples › iterate-over-hashmap
Java Program to Iterate over a HashMap
import java.util.HashMap; import java.util.Map.Entry; class Main { public static void main(String[] args) { // Creating a HashMap HashMap<String, String> languages = new HashMap<>(); languages.put("Java", "Enterprise"); languages.put("Python", "ML/AI"); languages.put("JavaScript", "Frontend"); System.out.println("HashMap: " + languages); // iterating through key/value mappings System.out.print("Entries: "); for(Entry<String, String> entry: languages.entrySet()) { System.out.print(entry); System.out.print(", "); } // iterating through keys System.out.print("\nKeys: "); for(String key: languages.keySet()) { System.out.print(key); System.out.print(", "); } // iterating through values System.out.print("\nValues: "); for(String value: languages.values()) { System.out.print(value); System.out.print(", "); } } }
EDUCBA
educba.com › home › software development › software development tutorials › java tutorial › java iterate map
Java Iterate Map | Learn How does Iteration Works in Map?
July 1, 2023 - Based on the requirement, we can iterate the map in any of the above ways. ... import java.util.HashMap; import java.util.Map; public class ForEachMapIteration { public static void main(String[] args) { // creating a hashmap object Map<Integer, String> names = new HashMap<>(); // adding key and values to hash map names.put(1, "Paramesh"); names.put(2, "Amardeep"); names.put(3, "Venkatesh"); names.put(4, "Ramesh"); names.put(5, "Suresh"); names.put(3, "Krishna"); names.put(4, "Rama"); names.put(5, "Rajitha"); // iterating key and value with forEach loop names.forEach((key, value) -> { System.out.println("ID =>" + key + " Name => " + value); }); } }
Call: +917738666252
Address: Unit no. 202, Jay Antariksh Bldg, Makwana Road, Marol, Andheri (East),, 400059, Mumbai
Medium
medium.com › @reetesh043 › mastering-map-iteration-in-java-a-comprehensive-guide-f64f12115d36
How To Iterate Map in Java. Introduction | by Reetesh Kumar | Medium
January 25, 2024 - With Java 8 and later, we can use streams to iterate through maps elegantly. // Method 3: Using Java Streams System.out.println("Method 3: Using Java Streams"); userMap.forEach((username, user) -> { System.out.println("Username: " + username + ", User: " + user); }); We can also iterate through keys or values separately.
Interview Kickstart
interviewkickstart.com › home › blogs › learn › how to iterate a map in java
How to Iterate a Map in Java | Interview Kickstart
March 29, 2026 - Java iterate map is a method of parsing through all key-value pairs in a database or page so that they can be modified and processed.
Medium
medium.com › @yadavsunil9699 › exploring-multiple-ways-to-iterate-through-maps-in-java-133441904b1e
Exploring Multiple Ways to Iterate Through Maps in Java | by Yadavsunil | Medium
September 8, 2023 - Map<Integer, String> colors = new TreeMap<>(); colors.put(1, "Red"); colors.put(2, "Green"); colors.put(3, "Blue"); colors.forEach((key, value) -> System.out.println("Color code: " + key + ", Color name: " + value)); ... Provides a clean and concise syntax for iterating through entries. Fits well with lambda expressions. ... When you want a shorter and more modern syntax for iterating through Map entries. Suitable for Java 8+ projects looking for improved code readability.
W3Schools
w3schools.com › java › java_howto_loop_through_hashmap.asp
Java How To Loop Through a HashMap
close() delimiter() findInLine() ... Java Server Java Syllabus Java Study Plan Java Interview Q&A ... Loop through the items of a HashMap with a for-each loop....
JanBask Training
janbasktraining.com › community › java › how do i efficiently iterate over each entry in a java map?
How do I efficiently iterate over each entry in a Java Map? | JanBask Training Community
April 18, 2025 - Cons: Slower due to repeated get() calls. In conclusion, the best way to iterate over a Java Map depends on the use case. If you need both keys and values, entrySet() is the most efficient.
Javatutorial
javatutorial.net › java-iterate-hashmap-example
Java Iterate through a HashMap Example | Java Tutorial Network
import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.Map.Entry; public class IterateHashMap { public static void main(String[] args) { Map<String, String> map = new HashMap<String, String>(); map.put("key1", "value1"); map.put("key2", "value2"); Iterator<Entry<String, String>> it = map.entrySet().iterator(); while (it.hasNext()) { Map.Entry<String, String> pair = (Map.Entry<String, String>) it.next(); System.out.println(pair.getKey() + " = " + pair.getValue()); } } }