diff --git a/mapstruct/pom.xml b/mapstruct/pom.xml
index 11c8d9b41e..9fe6ab6485 100644
--- a/mapstruct/pom.xml
+++ b/mapstruct/pom.xml
@@ -16,7 +16,7 @@
     <dependencies>
         <dependency>
             <groupId>org.mapstruct</groupId>
-            <artifactId>mapstruct-jdk8</artifactId>
+            <artifactId>mapstruct</artifactId>
             <version>${org.mapstruct.version}</version>
         </dependency>
         <dependency>
@@ -71,12 +71,12 @@
     </build>
 
     <properties>
-        <org.mapstruct.version>1.3.0.Final</org.mapstruct.version>
+        <org.mapstruct.version>1.4.0.Beta1</org.mapstruct.version>
         <springframework.version>4.3.4.RELEASE</springframework.version>
         <maven.compiler.source>1.8</maven.compiler.source>
         <maven.compiler.target>1.8</maven.compiler.target>
         <org.projectlombok.version>1.18.4</org.projectlombok.version>
-        <assertj.version>3.11.1</assertj.version>
+        <assertj.version>3.16.1</assertj.version>
     </properties>
 
 </project> 
diff --git a/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/dto/CompanyDTO.java b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/dto/CompanyDTO.java
new file mode 100644
index 0000000000..de3571e676
--- /dev/null
+++ b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/dto/CompanyDTO.java
@@ -0,0 +1,25 @@
+package com.baeldung.mapstruct.mappingCollections.dto;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class CompanyDTO {
+
+    private List<EmployeeDTO> employees;
+
+    public List<EmployeeDTO> getEmployees() {
+        return employees;
+    }
+
+    public void setEmployees(List<EmployeeDTO> employees) {
+        this.employees = employees;
+    }
+
+    public void addEmployee(EmployeeDTO employeeDTO) {
+        if (employees == null) {
+            employees = new ArrayList<>();
+        }
+
+        employees.add(employeeDTO);
+    }
+}
diff --git a/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/dto/EmployeeDTO.java b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/dto/EmployeeDTO.java
new file mode 100644
index 0000000000..04e5a1f180
--- /dev/null
+++ b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/dto/EmployeeDTO.java
@@ -0,0 +1,23 @@
+package com.baeldung.mapstruct.mappingCollections.dto;
+
+public class EmployeeDTO {
+
+    private String firstName;
+    private String lastName;
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+}
diff --git a/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/dto/EmployeeFullNameDTO.java b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/dto/EmployeeFullNameDTO.java
new file mode 100644
index 0000000000..10b97bfce4
--- /dev/null
+++ b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/dto/EmployeeFullNameDTO.java
@@ -0,0 +1,14 @@
+package com.baeldung.mapstruct.mappingCollections.dto;
+
+public class EmployeeFullNameDTO {
+
+    private String fullName;
+
+    public String getFullName() {
+        return fullName;
+    }
+
+    public void setFullName(String fullName) {
+        this.fullName = fullName;
+    }
+}
diff --git a/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapper.java b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapper.java
new file mode 100644
index 0000000000..5310c0454e
--- /dev/null
+++ b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapper.java
@@ -0,0 +1,11 @@
+package com.baeldung.mapstruct.mappingCollections.mapper;
+
+import com.baeldung.mapstruct.mappingCollections.dto.CompanyDTO;
+import com.baeldung.mapstruct.mappingCollections.model.Company;
+import org.mapstruct.Mapper;
+
+@Mapper(uses = EmployeeMapper.class)
+public interface CompanyMapper {
+
+    CompanyDTO map(Company company);
+}
diff --git a/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapperAdderPreferred.java b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapperAdderPreferred.java
new file mode 100644
index 0000000000..e5cc43074e
--- /dev/null
+++ b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapperAdderPreferred.java
@@ -0,0 +1,12 @@
+package com.baeldung.mapstruct.mappingCollections.mapper;
+
+import com.baeldung.mapstruct.mappingCollections.dto.CompanyDTO;
+import com.baeldung.mapstruct.mappingCollections.model.Company;
+import org.mapstruct.CollectionMappingStrategy;
+import org.mapstruct.Mapper;
+
+@Mapper(collectionMappingStrategy = CollectionMappingStrategy.ADDER_PREFERRED)
+public interface CompanyMapperAdderPreferred {
+
+    CompanyDTO map(Company company);
+}
diff --git a/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeFullNameMapper.java b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeFullNameMapper.java
new file mode 100644
index 0000000000..44d3961f2b
--- /dev/null
+++ b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeFullNameMapper.java
@@ -0,0 +1,20 @@
+package com.baeldung.mapstruct.mappingCollections.mapper;
+
+import com.baeldung.mapstruct.mappingCollections.dto.EmployeeFullNameDTO;
+import com.baeldung.mapstruct.mappingCollections.model.Employee;
+import org.mapstruct.Mapper;
+
+import java.util.List;
+
+@Mapper
+public interface EmployeeFullNameMapper {
+
+    List<EmployeeFullNameDTO> map(List<Employee> employees);
+
+    default EmployeeFullNameDTO map(Employee employee) {
+        EmployeeFullNameDTO employeeInfoDTO = new EmployeeFullNameDTO();
+        employeeInfoDTO.setFullName(employee.getFirstName() + " " + employee.getLastName());
+
+        return employeeInfoDTO;
+    }
+}
diff --git a/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeMapper.java b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeMapper.java
new file mode 100644
index 0000000000..45bf76c5a4
--- /dev/null
+++ b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeMapper.java
@@ -0,0 +1,19 @@
+package com.baeldung.mapstruct.mappingCollections.mapper;
+
+import com.baeldung.mapstruct.mappingCollections.dto.EmployeeDTO;
+import com.baeldung.mapstruct.mappingCollections.model.Employee;
+import org.mapstruct.Mapper;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+@Mapper
+public interface EmployeeMapper {
+
+    List<EmployeeDTO> map(List<Employee> employees);
+
+    Set<EmployeeDTO> map(Set<Employee> employees);
+
+    Map<String, EmployeeDTO> map(Map<String, Employee> idEmployeeMap);
+}
diff --git a/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/model/Company.java b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/model/Company.java
new file mode 100644
index 0000000000..f96e0b7aea
--- /dev/null
+++ b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/model/Company.java
@@ -0,0 +1,16 @@
+package com.baeldung.mapstruct.mappingCollections.model;
+
+import java.util.List;
+
+public class Company {
+
+    private List<Employee> employees;
+
+    public List<Employee> getEmployees() {
+        return employees;
+    }
+
+    public void setEmployees(List<Employee> employees) {
+        this.employees = employees;
+    }
+}
diff --git a/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/model/Employee.java b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/model/Employee.java
new file mode 100644
index 0000000000..db6809d53f
--- /dev/null
+++ b/mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/model/Employee.java
@@ -0,0 +1,28 @@
+package com.baeldung.mapstruct.mappingCollections.model;
+
+public class Employee {
+
+    private String firstName;
+    private String lastName;
+
+    public Employee(String firstName, String lastName) {
+        this.firstName = firstName;
+        this.lastName = lastName;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+}
diff --git a/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapperAdderPreferredUnitTest.java b/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapperAdderPreferredUnitTest.java
new file mode 100644
index 0000000000..ad0096f189
--- /dev/null
+++ b/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapperAdderPreferredUnitTest.java
@@ -0,0 +1,32 @@
+package com.baeldung.mapstruct.mappingCollections.mapper;
+
+import com.baeldung.mapstruct.mappingCollections.dto.CompanyDTO;
+import com.baeldung.mapstruct.mappingCollections.dto.EmployeeDTO;
+import com.baeldung.mapstruct.mappingCollections.model.Company;
+import com.baeldung.mapstruct.mappingCollections.model.Employee;
+import org.junit.jupiter.api.Test;
+import org.mapstruct.factory.Mappers;
+
+import java.util.Collections;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class CompanyMapperAdderPreferredUnitTest {
+
+    private CompanyMapperAdderPreferred companyMapper = Mappers.getMapper(CompanyMapperAdderPreferred.class);
+
+    @Test
+    void whenMappingToCompanyDTO_thenExpectCorrectMappingResult() {
+        Employee employee = new Employee("John", "Doe");
+        Company company = new Company();
+        company.setEmployees(Collections.singletonList(employee));
+
+        CompanyDTO result = companyMapper.map(company);
+
+        List<EmployeeDTO> employees = result.getEmployees();
+        assertThat(employees).hasSize(1);
+        assertThat(employees.get(0).getFirstName()).isEqualTo("John");
+        assertThat(employees.get(0).getLastName()).isEqualTo("Doe");
+    }
+}
\ No newline at end of file
diff --git a/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapperUnitTest.java b/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapperUnitTest.java
new file mode 100644
index 0000000000..a556c88ce5
--- /dev/null
+++ b/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapperUnitTest.java
@@ -0,0 +1,32 @@
+package com.baeldung.mapstruct.mappingCollections.mapper;
+
+import com.baeldung.mapstruct.mappingCollections.dto.CompanyDTO;
+import com.baeldung.mapstruct.mappingCollections.dto.EmployeeDTO;
+import com.baeldung.mapstruct.mappingCollections.model.Company;
+import com.baeldung.mapstruct.mappingCollections.model.Employee;
+import org.junit.jupiter.api.Test;
+import org.mapstruct.factory.Mappers;
+
+import java.util.Collections;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class CompanyMapperUnitTest {
+
+    private CompanyMapper companyMapper = Mappers.getMapper(CompanyMapper.class);
+
+    @Test
+    void whenMappingToCompanyDTO_thenExpectCorrectMappingResult() {
+        Employee employee = new Employee("John", "Doe");
+        Company company = new Company();
+        company.setEmployees(Collections.singletonList(employee));
+
+        CompanyDTO result = companyMapper.map(company);
+
+        List<EmployeeDTO> employees = result.getEmployees();
+        assertThat(employees).hasSize(1);
+        assertThat(employees.get(0).getFirstName()).isEqualTo("John");
+        assertThat(employees.get(0).getLastName()).isEqualTo("Doe");
+    }
+}
\ No newline at end of file
diff --git a/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeFullNameMapperUnitTest.java b/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeFullNameMapperUnitTest.java
new file mode 100644
index 0000000000..ba010a2bca
--- /dev/null
+++ b/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeFullNameMapperUnitTest.java
@@ -0,0 +1,26 @@
+package com.baeldung.mapstruct.mappingCollections.mapper;
+
+import com.baeldung.mapstruct.mappingCollections.dto.EmployeeFullNameDTO;
+import com.baeldung.mapstruct.mappingCollections.model.Employee;
+import org.junit.jupiter.api.Test;
+import org.mapstruct.factory.Mappers;
+
+import java.util.Collections;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class EmployeeFullNameMapperUnitTest {
+
+    private EmployeeFullNameMapper employeeMapper = Mappers.getMapper(EmployeeFullNameMapper.class);
+
+    @Test
+    void whenMappingToEmployeeFullNameDTOList_thenExpectCorrectMappingResult() {
+        Employee employee = new Employee("John", "Doe");
+
+        List<EmployeeFullNameDTO> result = employeeMapper.map(Collections.singletonList(employee));
+
+        assertThat(result).hasSize(1);
+        assertThat(result.get(0).getFullName()).isEqualTo("John Doe");
+    }
+}
\ No newline at end of file
diff --git a/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeMapperUnitTest.java b/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeMapperUnitTest.java
new file mode 100644
index 0000000000..dfb58252dc
--- /dev/null
+++ b/mapstruct/src/test/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeMapperUnitTest.java
@@ -0,0 +1,51 @@
+package com.baeldung.mapstruct.mappingCollections.mapper;
+
+import com.baeldung.mapstruct.mappingCollections.dto.EmployeeDTO;
+import com.baeldung.mapstruct.mappingCollections.model.Employee;
+import org.junit.jupiter.api.Test;
+import org.mapstruct.factory.Mappers;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class EmployeeMapperUnitTest {
+
+    private EmployeeMapper employeeMapper = Mappers.getMapper(EmployeeMapper.class);
+
+    @Test
+    void whenMappingToEmployeeDTOList_thenExpectCorrectMappingResult() {
+        Employee employee = new Employee("John", "Doe");
+
+        List<EmployeeDTO> result = employeeMapper.map(Collections.singletonList(employee));
+
+        assertThat(result).hasSize(1);
+        assertThat(result.get(0).getFirstName()).isEqualTo("John");
+        assertThat(result.get(0).getLastName()).isEqualTo("Doe");
+    }
+
+    @Test
+    void whenMappingToEmployeeDTOSet_thenExpectCorrectMappingResult() {
+        Employee employee = new Employee("John", "Doe");
+
+        Set<EmployeeDTO> result = employeeMapper.map(Collections.singleton(employee));
+
+        assertThat(result).hasSize(1);
+        assertThat(result.iterator().next().getFirstName()).isEqualTo("John");
+        assertThat(result.iterator().next().getLastName()).isEqualTo("Doe");
+    }
+
+    @Test
+    void whenMappingToEmployeeDTOMap_thenExpectCorrectMappingResult() {
+        Employee employee = new Employee("John", "Doe");
+
+        Map<String, EmployeeDTO> result = employeeMapper.map(Collections.singletonMap("1", employee));
+
+        assertThat(result).hasSize(1);
+        assertThat(result.get("1").getFirstName()).isEqualTo("John");
+        assertThat(result.get("1").getLastName()).isEqualTo("Doe");
+    }
+}
\ No newline at end of file