Java Constructor Question

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Hello WP, it has been a very long time... I have a question regarding constructors in Java. In my Java class in college we had a homework assignment that required us to create a class called employee with the attributes of name and salary. I completed the assignment and already received a grade however the instructor said that I need to add a constructor which brings me to my question. Given the following code snippit:

You can have multiple constructors, so there could not be be a "best one" but an instance of the class without a true "index" value that will be unique could be considered a bad constructor. For example if I were to build an array of that class, and use the salary constructor, and some of them have the same salary, then those are not representing unique employees.


This constructor that you already used is the best one:
employee(String fN, String lN, double sal) {
firstName = fN;
lastName = lN;
salary = sal;
}

You set the two most important fields and the salary field.

The next assignment will probably use this class, but have fields for department, position, etc. So expect that to have a constructor that sets those fields, and then a "super" call relaying name and salary (this is what I suspect).

It won't be that hard.

A constructor's job is to put the newly created object into a fully-initialized state where it can be used. It will create any contained (HASA) objects, initialize fields, and so on. Arguments to the constructor tell the constructor values that it can't otherwise know.

Thanks guys,


@ SickInDaHead:
Yeah I believe you are correct that the next assignment wants us to extend this class for department, position and things like that. I believe he also wants us to make an array and have it populate with several employees but I will have to re-read the assignment to make sure. I'm sure I'll be running back to WP for more re-assurance on that assignment as well.

With your code - you never actually set the variables for firstName, lastName, or salary. You don't even have any methods to use in that object to set them - so, you have uninitialized variables that you're trying to read from. If you actually tried to write code that used that object you'd pretty quickly see the problem with that. In fact, I'm somewhat surprised that you actually got that to compile.

You want to create multiple constructors for every logical possibility. So - for each employee you add to the program, you would have certain information at the very least you'd have their name, and salary. But, you might not have their home address at the time you add them to the program, you may only get that information once they start their first day and fill out forms. So, what you would do is create a constructor that required you to input all the information you *do* have (first and last name, salary) and then fill in "default" information for the information you may not have (ie. setting the homeAddress variable to = ""). You need to have the variable initialized, because if you try to use a variable that isn't initialized you get an error in your code - so you set it to a value that the code can work with, but that practically means nothing.