Merge pull request #5377 from MherBaghinyan/BAEL-2244

Bael 2244

core-java-collections/pom.xml

@@ -68,6 +68,11 @@
 		    <artifactId>commons-exec</artifactId>
 		    <version>1.3</version>
 		</dependency>
+        <dependency>
+            <groupId>one.util</groupId>
+            <artifactId>streamex</artifactId>
+            <version>0.6.5</version>
+        </dependency>
 		        
     </dependencies>
 

core-java-collections/src/main/java/com/baeldung/map/java_8/MergeMaps.java

@@ -0,0 +1,105 @@
+package com.baeldung.map.java_8;
+
+import com.baeldung.sort.Employee;
+import one.util.streamex.EntryStream;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class MergeMaps {
+
+    private static Map<String, Employee> map1 = new HashMap<>();
+    private static Map<String, Employee> map2 = new HashMap<>();
+
+    public static void main(String[] args) {
+
+        initialize();
+
+        mergeFunction();
+
+        streamConcat();
+
+        streamOf();
+
+        streamEx();
+
+        streamMerge();
+    }
+
+    private static void streamMerge() {
+
+        Map<String, Employee> map3 = map2.entrySet()
+                .stream()
+                .collect(
+                        Collectors.toMap(
+                                Map.Entry::getKey,
+                                Map.Entry::getValue,
+                                (v1, v2) -> new Employee(v1.getId(), v2.getName()),
+                                () -> new HashMap<>(map1)
+                        )
+                );
+
+        System.out.println(map3);
+    }
+
+    private static void streamEx() {
+        Map<String, Employee> map3 = EntryStream.of(map1)
+                .append(EntryStream.of(map2))
+                .toMap((e1, e2) -> e1);
+
+        System.out.println(map3);
+
+    }
+
+    private static void streamOf() {
+        Map<String, Employee> map3 = Stream.of(map1, map2)
+                .flatMap(map -> map.entrySet().stream())
+                .collect(
+                        Collectors.toMap(
+                                Map.Entry::getKey,
+                                Map.Entry::getValue,
+                                (v1, v2) -> new Employee(v1.getId(), v2.getName())
+                        )
+                );
+
+        map3.entrySet().forEach(System.out::println);
+    }
+
+    private static void streamConcat() {
+        Map<String, Employee> result = Stream.concat(map1.entrySet().stream(), map2.entrySet().stream()).collect(Collectors.toMap(
+                Map.Entry::getKey,
+                Map.Entry::getValue,
+                (value1, value2) -> new Employee(value2.getId(), value1.getName())
+        ));
+
+        result.entrySet().forEach(System.out::println);
+    }
+
+    private static void mergeFunction() {
+        Map<String, Employee> map3 = new HashMap<>(map1);
+
+        map2.forEach(
+                (key, value) -> map3.merge(key, value, (v1, v2) ->
+                        new Employee(v1.getId(), v2.getName()))
+        );
+
+        map3.entrySet().forEach(System.out::println);
+    }
+
+
+    private static void initialize() {
+        Employee employee1 = new Employee(1L, "Henry");
+        map1.put(employee1.getName(), employee1);
+        Employee employee2 = new Employee(22L, "Annie");
+        map1.put(employee2.getName(), employee2);
+        Employee employee3 = new Employee(8L, "John");
+        map1.put(employee3.getName(), employee3);
+
+        Employee employee4 = new Employee(2L, "George");
+        map2.put(employee4.getName(), employee4);
+        Employee employee5 = new Employee(3L, "Henry");
+        map2.put(employee5.getName(), employee5);
+    }
+
+}