Use java 8 stream api to do deep copy of array list but get build time error

I use lombok library in my spring-boot project's model classes.

@Data
@Builder
public class Employee {

    private String fullname;
    private long someNumber;
    private boolean isManager;
}

In another class, I have a list of employees:

List<Employee> employeeList = getListOfEmployees();

I would like to create a deep copy of the employeeList, the following things are what I tried:

step 1. I create a copy constructor in Employee class:

@Data
@Builder
public class Employee {

    private String fullname;
    private long someNumber;
    private boolean isManager;

    // copy constructor
    public Employee(Employee employee) {
        this.fullname = employee.fullname;
        this.someNumber = employee.someNumber;
        this.isManager = employee.isManager;
    }
}

step 2. I use Java 8 stream API to create a deep copy of the list of employees:

List<Employee> employeeListCopy = employeeList.stream().map(Employee::new).collect(Collectors.toList());

But when I build my sprint-boot project, I got error:

Error:(13, 1) java: constructor Employee in class com.my.webapp.model.Employee cannot be applied to given types;
  required: com.my.webapp.Employee
  found: java.lang.String,long,boolean
  reason: actual and formal argument lists differ in length

Why? How to get rid of this error for my deep copy?

The problem is not in the Stream API, but in lombok. When you use @Builder, there will be a call to a constructor:

public Employee build() {
      return new Employee(fullname, someNumber, isManager);
}

from within EmployeeBuilder (that lombok will generate). Since you have already provided a constructor, lombok will not generate another one (i.e.: lombok will only generate the needed constructor for the Builder IFF there is not a constructor already defined). The solution is rather simple, add @AllArgsConstructor to your class.

In general, I personally, am not a fan of @Builder, I use @Accessors(chain = true) instead:

@Setter
@Getter
@Accessors(chain = true)
static class Employee {

    private String fullname;
    private long someNumber;
    private boolean isManager;

    public Employee() {

    }

    // copy constructor
    public Employee(Employee employee) {
        fullname = employee.fullname;
        someNumber = employee.someNumber;
        isManager = employee.isManager;
    }
}

And you can do:

Employee emp = new Employee()
        .setFullname("")
        .setManager(false)
        .setSomeNumber(2L);