CODEWITHSUNDEEP
javaarraylist
Snar3
Snar3

Reputation: 68

Sorting through ArrayList of Objects, Add given Instance to ArrayList of given instances issue

I'm getting the error

no suitable method found for add(Object), method Collected.add(Student is not applicable)

when I try the following code. I swear I've done it this way before? So confused. Appreciate any insights. Cheers

    //Sort and display list of Student objects by sortBy (surname or id)
public static void sortAndDisplayStudents(String sortBy, ArrayList<Object> objList) {
    ArrayList<Student> students = new ArrayList<>();

    //Add all Objcets in objList that are a Student
    for(Object s: objList) {
        if(s instanceof Student) {
            students.add(s);
        }
    }
}

Upvotes: 1

Views: 53

Answers (2)

Cardinal System
Cardinal System

Reputation: 3422

Just to avoid any errors, change the way you construct the array list:

ArrayList<Student> students = new ArrayList<>(); 
ArrayList<Student> students = new ArrayList<Student>();

As for the add method, you want to cast to the passing object otherwise the JVM will not know that the object being passed is instanceof Student:

students.add((Student) s);

Also, you should get an IDE, they usually solve these problems before they happen.

Upvotes: 0

OLIVER.KOO
OLIVER.KOO

Reputation: 5993

ArrayList<Student> students = new ArrayList<>(); shows that students is a ArrayList that contain the Object Student.

Therefore you need to cast your s Object to Student before adding it to the students list. like such students.add((Student)s); Here is how you cast Object in Java.

Upvotes: 2

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