如何重构else-如果选择正确的构造函数

Question

I'm on the way to implement Factory pattern in my app and work going fine except block of code below (i have another one, much larger for another class). Is there any way to refactor this "jungle"-structure? Thanks in advance!

private Goal createLocalTaskInstance(HashMap<String, Object> goalDetails){
    Goal goal = null;

    if (goalDetails.get("description") == null &&
            goalDetails.get("endDate") == null){
        goal = new Task(String.valueOf(goalDetails.get("title")));

    } else if (goalDetails.get("description") != null &&
            goalDetails.get("endDate") == null) {
        goal = new Task(String.valueOf(goalDetails.get("title")),
                String.valueOf(goalDetails.get("description")));

    } else if (goalDetails.get("description") == null &&
            goalDetails.get("endDate") != null) {
        goal = new Task(String.valueOf(goalDetails.get("title")),
                        (Date) goalDetails.get("endDate"));

    } else if (goalDetails.get("description") != null &&
            goalDetails.get("endDate") != null){
        goal = new Task(String.valueOf(goalDetails.get("title")),
                String.valueOf(goalDetails.get("description")),
                (Date) goalDetails.get("endDate"));
    }
    return goal;
}

Answer 1

I would suggest that you simply call the default constructor (with all three arguments) regardless of some of them being null, and then simply do a null check in the constructor. It would then look something like this:

goal = new Task(String.valueOf(goalDetails.get("title"),
                goalDetails.get("description"), 
                goalDetails.get("endDate"));

And the Task class:

public class Task {
    private String title;
    private String description;
    private Date endDate;

    public Task(String title, String description, Date endDate) {
        this.title = title;
        if(description != null) {
            this.description = description;
        }
        if(endDate != null) {
            this.endDate = endDate;
        }
    }
}