Merge two maps with Java 8

dardy :

I have two maps like this:

map1 = new Map<String, MyObject>();
map2 = new Map<String, MyObject>();

MyObject {
   Integer mark1;
   Integer mark2;
}

What I want to do to is to merge the two maps into a map3 <String, MyObject> like this:

1. If map1.place is not in map2.place, then I add the entry to map3.
2. same if map2.place is not in map1.place, I add the entry to map3.
3. if map1.place is in map2.place, then I add this entry:
   • map1.place, (map1.mark1, map2.mark2)

I have read about flatMap, but I really have a hard time using it. Any clue how to do this?
Thanks!!

Ash :

Here is what I think would work

Map<String, MyObj> map3 = new HashMap<>(map1);
map2.forEach(
    (key, value) -> map3.merge(key, value, (v1, v2) -> new MyObject(v1.mark1,v2.mark2))
);

The merge function is what is taking care of your scenario 3, in that if the key already exists, it creates a new MyObject with v1.mark1 and v2.mark2

Guess you like

Origin http://10.200.1.11:23101/article/api/json?id=452252&siteId=1

Merge two maps with Java 8

Java 8 streams - merge a collection of Maps

Merge maps from a list of maps java8

Efficiently Merge two ArrayLists of Maps

How to interleave (merge) two Java 8 Streams?

Java 8: how to 'JOIN' two Maps having the same Keys?

Is there a way to merge two for loops using Streams in java 8?

How to merge two nested maps with same keys and keep the values

How to filter two maps and make third map by using Lamda expression java 8

Java8 Collecting maps

Custom Sort Maps in Java 8

Java 8 streams maps with parameters

How to merge two list of POJOS using stream JAVA 8 modifying some values when necessary

Join 2 maps Java 8 using streams

Mapping Nested Lists to Nested Maps in Java 8

Mapping Nested Lists to Nested Maps in Java 8

[java basics] array merge, merge two arrays into one array

Java---Merge two ascending and ordered arrays

Merge two sorted linked lists-Java

Merge two sorted linked lists (java)

Merge two Java Maven projects into one

Java two arrays merge into one array

How to create a map of maps from a list of maps with Java 8 streaming api

Java 8 in merge Map Sao operation of () usage

Use of the merge() method of Map in Java 8

creating nested maps with nested properties from List, stream, Java 8

How can I sort a list of maps using Java 8?

"Prove safety offer" - merge two sorted lists (Java)

Leetcode (Java) -88. Merge two ordered arrays

Record again java Stream API merge two operations List