Java 8 Streams hashmap

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I need perform an hashmap iteration using Java 8 streams. I need to iterate over an hashmap. Check whether a particular key ("new") does not have null or empty values, copy that value to a variable (String val1) of type string. Then again check for another key for ex:"old" and then copy that value to a variable (String val2) of type string and call the main method where i need to send these 2 values (val1, val2). This has to be done with in hashmap iteration. Can you please help me on this.

The code:

    .filter(s -> { 
        if (s.getKey().contains("abc") && !s.getValue().equals("") && s.getValue()!=null) {
            String val1 = s.getValue;
            if (s.getKey().contains("bb")) {
                String val2 = s.getValue(); //call the function
        else {

Need to be done using Java 8

for(Map.Entry e : map1.entrySet()) {
                if(e.containsKey("new")&& !e.getValue().equals("")){
                    String val1 = (String) e.getValue();

                    if(e.containsKey("old")&& !e.getValue().equals("")){
                        String val2 = (String) e.getValue();

                        //call the function-- This is boolean
                        if(validateMethod(val1, val2)){ // if true
                            Map<String, String> map2 = new HashMap<>();




Hashmap with Streams in Java 8 Streams to collect value of Map , Hashmap with Streams in Java 8 Streams to collect value of Map. Map<Integer, List> id1 = new HashMap<Integer,List>(); I inserted some values into both hashmap. Welcome to Java 8 series. In this tutorial, you will learn about how to convert a Stream to a HashMap in Java 8. If you would like to learn more about Java Stream operations.Please check out this link. In order, to convert a stream to a collection we have to use Collectors api provided in Java 8. So we have to import the below package

Java 8 – Filter a Map examples –, Few Java examples to show you how to filter a Map with Java 8 stream API. With Java 8, you can convert a Map. entrySet() into a stream , follow by a filter() and collect() it.   With the release of Java 8, we can use sorted() method of Stream class by passing comparator objects Sorting HashMap by its Keys in Java 1.8 use comparingByKey() method of Map.Entry class which returns comparator object to compare Map entry by its keys

Try it with this:


From this point, you can manage. Stream consists of Entry<Key,Value> so you can check whatever you want to.

How to compare two hashmaps in Java, How do I compare two maps by their keys in Java 8? The fact that Streams exist doesn't mean you should use them everywhere. Having streams inside streams is a sign that things have gone off the rails badly. Try doing this without streams and it'll be much easier to refactor it into maintainable code.

How to use filter + map + collect + Stream in Java , Java 8 – Filter Map by Keys. import java.util.Map; import java.util.HashMap; import; public class Example { public static void  In Java 8 – How to sort a Map? On Crunchify we have written almost ~400 java tutorials and this one is an addition to Java8 category. I love Java collection and have multiple tutorials on How to iterate through Map and List, LinkedList, JSONArray and lot more. In this tutorial we will go over Best way to sort HashMap by Key and Value in Java8.

Java 8 - Filter a Map by keys and values, groupingBy() methods using Java 8 Stream APIs. Convert Java 8 example to convert list to map using stream APIs. HashMap.merge( 1245 )​  Iterate by using the forEach method of the Map interface. We can use foreach default method of the Map interface with Lambda expression to iterate over a HashMap in Java 8, for example: Map<Integer, String> itemsMap = new HashMap<>(); itemsMap.put(1, "One"); itemsMap.put(2, "Two");

Java 8 - Convert stream to Map, 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. import java.util.​HashMap;. import java.util.Map;. import;. class MapUtils. Let's see ways of obtaining different Collections from a Map, which we can then pivot into a Stream: Map<String, Integer> someMap = new HashMap<>(); We can obtain a set of key-value pairs: Set<Map.Entry<String, Integer>> entries = someMap.entrySet(); We can also get the key set associated with the Map: Set<String> keySet = someMap.keySet();

  • Sounds like homework which should be done by your own
  • Indeed. What I do not understand is what is the point of posting on SO when the first match of a google search give an appropriate answer.
  • Hello Renuka, can you post some your effort(try google with "java 8 streams hashmap iterators").
  • I know there is some mistake in this snippet, but here is what i am looking for map1.entrySet().stream().filter(s->{ if(s.getKey().contains("abc")&&!s.getValue().equals("")&& s.getValue()!=null) { String val1 = s.getValue; if(s.getKey().contains("bb")) { String val2 = s.getValue(); //call the function callFunction(val1,val2); } }else { } });
  • Post your code in the question and format it. It's hard to read code in comments.
  • Your code does nothing, because map2 is never used, so it's not accessible after the if and the for
  • And containsKey is not a method of Map.Entry
  • This does not answer the question, and if it does, you can bet this answer exists already, in which case you should flag as a duplicate.