Java : Getting unchecked cast required warning

Question

I am trying to write a generic class definition for class UniCourse that stores students that are registered in the course.

It creates UniCourse objects that use student emails as identities (e.g. abc123 :: (Type String), or student Id :: (Type Integer).

I'm getting this warning:

unchecked cast required: T[] found: java.lang.Object[]

Could someone explain what this means and how to fix this?

public class UniCourse<T> {
    private T[] students;

    public UniCourse (int size) {
    T[] students = (T[]) new Object[size];
  }
}

Why don't you create a `Student` class and create a `Student[]` array instead? — QBrute, Sep 21 '19 at 13:46
@QBrute explained above is like a prompt. I need to create a generic class. — user12099607, Sep 21 '19 at 13:52
Possible duplicate of [How to create a generic array in Java?](https://stackoverflow.com/questions/529085/how-to-create-a-generic-array-in-java) — Michał Krzywański, Sep 21 '19 at 14:27

Paku580 · Answer 1 · 2019-09-21T14:56:22.697

One Solution would be to create your own Student Class which holds an array of your data as an Object. Your Student Class could look like this:

public class Student<T> {
    protected Object[] data;

    public Student (int size) {
    this.data = new Object[size];
  }
}

Then in your UniCourse Class you could create a Constructor like this:

public UniCourse(int size) {
  this.students = new Student<T>(size);
}

And finally you can call your Constructor with this line:

UniCourse<Integer> uniCourse = new UniCourse<Integer>(20);

To access the data Array created in your Student class you can simply do something like this:

this.students.data;

1 Answers1