6 ways to iterate or loop a Map in Java

Damith

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There are multiple ways to iterate or loop a Map in Java.

Using foreach in Java 8

If you using Java 8 this is the easiest way to loop the Map.

// {
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
public class Main {
public static void main(String[] args) {
// }
        Map<Integer, String> customers = new HashMap<>();
        customers.put(1, "Jhon");
        customers.put(2, "Smith");
        customers.put(3, "Sally");
        System.out.println("Using foreach in Java 8");
        customers.forEach((id, name) -> {
            System.out.println("Key : " + id + " value : " + name);
        });
//{
}
}
//}

Using stream() in Java 8

This is also using in Java 8. If you want to filter some data while looping this is one of best way to do that.

// {
        Map<Integer, String> customers = new HashMap<>();
        customers.put(1, "Jhon");
        customers.put(2, "Smith");
        customers.put(3, "Sally");
        System.out.println("");
        customers.entrySet().stream().forEach(e ->
                System.out.println("Key : " + e.getKey() + " value : " + e.getValue())
        );
//{

Using entrySet()

Using keySet()

Using iterator through map

This way is more suitable for when you need to remove some data while iterating.

// {
    Map<Integer, String> customers = new HashMap<>();
        customers.put(1, "Jhon");
        customers.put(2, "Smith");
        customers.put(3, "Sally");
        Iterator<Map.Entry<Integer, String>> iterator = customers.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry entry = iterator.next();
            System.out.println("Key : " + entry.getKey() + " value : " + entry.getValue());
        }
//{

Using iterator through the KeySet

// {
    Map<Integer, String> customers = new HashMap<>();
        customers.put(1, "Jhon");
        customers.put(2, "Smith");
        customers.put(3, "Sally");
        Iterator<Integer> iterator = customers.keySet().iterator();
        while (iterator.hasNext()) {
            Integer key = iterator.next();
            System.out.println("Key : " + key + " value : " + customers.get(key));
        }
//{

Original post :- http://mydevgeek.com/6-ways-iterate-loop-map-java/

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Using foreach in Java 8

Using stream() in Java 8

Using entrySet()

Using keySet()

Using iterator through map

Using iterator through the KeySet

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