Map iterate java 8

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Map iterate java 8

Scrum! ScrumMastery If you need to iterate over the elements in a Map in Java 8, this source code shows how to do it: Map map = new HashMap(); map.put("first_name", "Alvin"); map.put("last_name", "Alexander"); // java 8 map.forEach((k,v)->System.out.println("key: " + k + ", value: " + v)); This approach uses an anonymous function -- also known as a lambda -- and it's similar to the approach used to traverse a Map in Scala. How to iterate a Java 8 Map: A complete example The following complete example shows how to iterate over all of the elements in a Java Map (or HashMap) using both a) the Java 8 style and b) the type of code you had to use prior to Java 8: package java8_tests; import java.util.HashMap; import java.util.Map; public class IterateOverJava8Map { public static void main(String[] args) { Map map = new HashMap(); map.put("first_name", "Alvin"); map.put("last_name", "Alexander"); // java 8 map.forEach((k,v)->System.out.println("key: " + k + ", value: " + v)); // prior to java 8 for (Map.Entry entry : map.entrySet()) { System.out.println("key: " + entry.getKey() + ", value: " + entry.getValue()); } } } As a quick summary, if you needed to see how to iterate over the elements in a Map/HashMap in Java 8, I hope this is helpful. Java 8 Convert Map to List :- In this tutorial, we will learn to convert map to list using Stream API. Problem Statement :- Given a map of Integer as a key and String as a Value convert it to the list, containing all the values of Map. Let's see the implementation of above problem in java 7 and in java 8. Java 7 :- To implement this, iterate through the set of map's Entry object and add it's value to newly created List object. public static void main(String[] args){ Map map = new HashMap(); map.put(1,"Robert"); map.put(2,"Martin"); map.put(3,"Jack"); List list = new ArrayList(); Set set = map.entrySet(); Iterator iterate = set.iterator(); while(iterate.hasNext()){ list.add(iterate.next().getValue()); } for(String s : list){ System.out.println(s); } } Java 8 :- To implement this, we will use stream's map() method. public static void main(String[] args){ Map map = new HashMap(); map.put(1,"Robert"); map.put(2,"Martin"); map.put(3,"Jack"); List list = map.entrySet().stream().map( v -> v.getValue()).collect(Collectors.toList()); list.forEach( v -> System.out.println(v)); } Result :- Robert Martin Jack Reference :- Stream's map() JavaDocs That's all for Java 8 Convert Map to List. If you liked it, please share your thoughts in comments section and share it with others too. Looping over a Map in Java. In this post, we look at four different ways we can iterate through a map in Java. As of Java 8, we can use the forEach method as well as the iterator class to loop over a map. How to Iterate Map Entries (Keys and Values)Map map = new HashMap(); for (Map.Entry entry : map.entrySet()) { System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue()); } How to Iterate Map Keys OnlyMap map = new HashMap(); for (Integer key : map.keySet()) { System.out.println("Key = " + key); } How to Iterate Map Values Onlyfor (Integer value : map.values()) { System.out.println("Value = " + value); } Related: How to loop through an ArrayLists in Java Using Iterator Using Generics:Map map = new HashMap(); Iterator entries = map.entrySet().iterator(); while (entries.hasNext()) { Map.Entry entry = entries.next(); System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue()); } Without Generics:Map map = new HashMap(); Iterator entries = map.entrySet().iterator(); while (entries.hasNext()) { Map.Entry entry = (Map.Entry) entries.next(); Integer key = (Integer)entry.getKey(); Integer value = (Integer)entry.getValue(); System.out.println("Key = " + key + ", Value = " + value); } Iterating over keys and searching for valuesMap map = new HashMap(); for (Integer key : map.keySet()) { Integer value = map.get(key); System.out.println("Key = " + key + ", Value = " + value); } Using Java 8 ForEachMap items = new HashMap(); items.put("key 1", 1); items.put("key 2", 2); items.put("key 3", 3); items.forEach((k,v)->System.out.println("Item : " + k + " Count : " + v)); The Java forEach() method is a utility function to iterate over a collection such as (list, set or map) and stream. It is used to perform a given action on each the element of the collection.The forEach() method has been added in following places:Iterable interface ? This makes Iterable.forEach() method available to all collection classes except MapMap interface ? This makes forEach() operation available to all map classes.Stream interface ? This makes forEach() and forEachOrdered() operations available to all types of stream.1. Iterable forEach()1.1. forEach() MethodThe given code snippet shows the default implementation of forEach() method in Iterable interface.Internally it uses the enhanced for-loop. So using the new for-loop will give the same effect and performance as forEach() method. default void forEach(Consumer

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