Question

a student class is to be created that will include private instance variables:

• first_name
• last_name
• age
• grad_year

given these instance variables, which of the following constructor headers fit this class best?

option 1:
public student(string f, string l, int a, int gy)

option 2:
private student()

option 3:
public static student(string f, string l, int a, int gy)

which option correctly fills in the missing code?

• option 1
• option 3
• option 2

Explanation:

🆕 New Concept Discovered: Object-Oriented Constructors in Java
Setting up initial values for a new object.

Step 1: Analyze the Instance Variables

The Student class requires four private instance variables:

• first_name (typically a String)
• last_name (typically a String)
• age (typically an int)
• grad_year (typically an int)

A standard constructor should accept parameters to initialize all of these instance variables when a new Student object is created.

Step 2: Evaluate Constructor Rules in Java

In Java, constructors must follow specific syntax rules:

1. Access Modifier: Usually public so other classes can instantiate the object.
2. No Return Type: Constructors do not have a return type (not even void).
3. No static Keyword: Constructors cannot be declared as static because they are used to create individual, non-static instances of a class.
4. Name: Must match the class name exactly (Student).

Step 3: Compare the Options

• Option 1: public Student(String f, String l, int a, int gy)
• Correct. It is public, has no return type, does not use static, and provides parameters matching the types of the four instance variables.
• Option 2: private Student()
• Incorrect. It is marked private (which prevents normal instantiation from outside the class) and takes no parameters, leaving the required instance variables uninitialized.
• Option 3: public static Student(String f, String l, int a, int gy)
• Incorrect. Constructors cannot be declared static.

Answer:

Option 1