[stream-map-object] Create List of Object From Another Type Using Java 8 (#14716)

core-java-modules/core-java-collections-list-5/src/test/java/com/baeldung/java/streamtoanotherlist/CreateListOfDifferentTypeUsingStreamUnitTest.java

@@ -0,0 +1,114 @@
+package com.baeldung.java.streamtoanotherlist;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import org.assertj.core.util.Lists;
+import org.junit.jupiter.api.Test;
+
+import lombok.Getter;
+
+@Getter
+class Employee {
+    private final String name;
+    private final Set<String> hobbies = new HashSet<>();
+    private final String email;
+    private String department;
+
+    public Employee(String name, String email, Collection<String> hobbies) {
+        this.name = name;
+        this.email = email;
+        this.hobbies.addAll(hobbies);
+    }
+}
+
+class TennisPlayerCandidate {
+    private final String name;
+    private final String email;
+    private final Boolean confirmed = Boolean.FALSE;
+
+    public TennisPlayerCandidate(String name, String email) {
+        this.name = name;
+        this.email = email;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (!(o instanceof TennisPlayerCandidate))
+            return false;
+
+        TennisPlayerCandidate that = (TennisPlayerCandidate) o;
+
+        if (!Objects.equals(name, that.name))
+            return false;
+        return Objects.equals(email, that.email);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = name != null ? name.hashCode() : 0;
+        result = 31 * result + (email != null ? email.hashCode() : 0);
+        return result;
+    }
+}
+
+public class CreateListOfDifferentTypeUsingStreamUnitTest {
+    private final static List<Employee> EMPLOYEES = Lists.newArrayList(
+      // @formatter:off
+      new Employee("Kai", "kai@company.com", Lists.newArrayList("Football", "Reading", "Chess")),
+      new Employee("Eric", "eric@company.com", Lists.newArrayList("Tennis", "Baseball", "Singing")),
+      new Employee("Saajan", "saajan@company.com", Lists.newArrayList("Tennis", "Baseball", "Singing")),
+      new Employee("Kevin", "kevin@company.com", Lists.newArrayList("Dancing", "Computer Games", "Tennis")),
+      new Employee("Amanda", "amanda@company.com", Lists.newArrayList("Painting", "Yoga", "Dancing"))
+      //@formatter:on
+    );
+
+    private final static List<TennisPlayerCandidate> EXPECTED = Lists.newArrayList(
+      // @formatter:off
+      new TennisPlayerCandidate("Eric", "eric@company.com"),
+      new TennisPlayerCandidate("Saajan", "saajan@company.com"),
+      new TennisPlayerCandidate("Kevin", "kevin@company.com")
+      //@formatter:on
+    );
+
+    @Test
+    void whenUsingStreamForEachFillingAnotherList_thenGetExpectedResult() {
+        List<TennisPlayerCandidate> result = new ArrayList<>();
+        EMPLOYEES.forEach(e -> {
+            if (e.getHobbies()
+              .contains("Tennis")) {
+                result.add(new TennisPlayerCandidate(e.getName(), e.getEmail()));
+            }
+        });
+
+        assertEquals(EXPECTED, result);
+    }
+
+    @Test
+    void whenUsingStreamMap_thenGetExpectedResult() {
+        List<TennisPlayerCandidate> result = EMPLOYEES.stream()
+          .filter(e -> e.getHobbies()
+            .contains("Tennis"))
+          .map(e -> new TennisPlayerCandidate(e.getName(), e.getEmail()))
+          .collect(Collectors.toList());
+        assertEquals(EXPECTED, result);
+    }
+
+    @Test
+    void whenUsingCollectorMapping_thenGetExpectedResult() {
+        List<TennisPlayerCandidate> result = EMPLOYEES.stream()
+          .filter(e -> e.getHobbies()
+            .contains("Tennis"))
+          .collect(Collectors.mapping(e -> new TennisPlayerCandidate(e.getName(), e.getEmail()), Collectors.toList()));
+        assertEquals(EXPECTED, result);
+    }
+}