Problem 225

Constructors

It is time we start to complicate the creation of classes.

Think about creating an instance of an object. And then assigning values to its fields.

Student student = new Student();
student.firstName = "Frank";
student.lastName = "Smith";
student.birthYear = 1988;

Wouldn’t it be nice to include all that on one line?

You can.

All you need is a constructor as part of your class to be able to take the specific data and automatically assign the data to the object’s fields.

Constructors

It is proper form to always include a constructor when creating a class. Essentially, a constructor is just a method that takes arguments and assigns them to the object’s fields.

For ourStudent class, the constructor would look like this:

class Student {
	.
	.
	.
	
	public Student(String firstName, String lastName, int birthYear) {
		this.firstName = firstName;
		this.lastName = lastName;
		this.birthYear = birthYear;
	}
	
	.
	.
	.
}

The this keyword comes in handy to differentiate between the parameter variable and the current (this) objects field name.

Now, when we create an instance of a Student, we can assign the relevant info when it is created.

Student student = new Student("Frank", "Smith", 1988);

Just like any other method, it is important we know the order of the required parameters.