Hashmap with Streams in Java 8 Streams to collect value of Map

Question

Let consider a hashmap

Map id1 = new HashMap();

I inserted some values into both hashmap.

For

Answer 1

What you need to do is create a Stream out of the Map's .entrySet():

// Map --> Set> --> Stream>
map.entrySet().stream()

From the on, you can .filter() over these entries. For instance:

// Stream> --> Stream>
.filter(entry -> entry.getKey() == 1)

And to obtain the values from it you .map():

// Stream> --> Stream
.map(Map.Entry::getValue)

Finally, you need to collect into a List:

// Stream --> List
.collect(Collectors.toList())

If you have only one entry, use this instead (NOTE: this code assumes that there is a value; otherwise, use .orElse(); see the javadoc of Optional for more details):

// Stream --> Optional --> V
.findFirst().get()