Java error: incompatible types: Object[] cannot be converted to Student[]

Question

I don't know how do I tackle this compilation error.

my code is

public ArrayList<Student> SortOnCGPA(ArrayList<Student> stu){        
        Student sorStu[] = stu.toArray();
        Arrays.sort(sorStu, new StuDescend());
        stu = new ArrayList(Arrays.asList(sorStu));
        return stu;
    }

and the error is:

JavaPQ.java:23: error: incompatible types: Object[] cannot be converted to Student[]
        Student sorStu[] = stu.toArray();
                                      ^
Note: JavaPQ.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
1 error

I know that the "toArray()" method will return an array of type Object. I don't know how to typecast it to Student[] or any alternative solution. Thanks for for your help.

I used a loop to solve my problem

public ArrayList<Student> SortOnCGPA(ArrayList<Student> stu){        
        Student sorStu[] =new Student[stu.size()];
        Iterator it = stu.iterator();
        int i = 0;
        while(it.hasNext()){
            sorStu[i] = new Student((Student)it.next());
            i++;
        }
        Arrays.sort(sorStu, new StuDescend());
        stu = new ArrayList(Arrays.asList(sorStu));
        return stu;
    }

But I wanted to know how do I use the ".toArray()" method of the collections framework.

Why are you converting to an array anyway? What's wrong with `List.sort`? Or `stu.stream().sorted(new StuDescend()).collect(toList())`? — Andy Turner, Sep 04 '18 at 08:35
@AndrewTobilko you may be interested in [this article](https://shipilev.net/blog/2016/arrays-wisdom-ancients/). TL;DR: `new Student[0]` was found to be better. — Andy Turner, Sep 04 '18 at 08:37
@AndrewTobilko (`Collections.sort` delegates to `List.sort`) — Andy Turner, Sep 04 '18 at 08:38
By using toArray() JVM will not blindly know your type of array. So you need to pass your typed array e.g. Student[] stdArr = new Student[stu.size()]; . Then it will create your desired output. — Vivek, Sep 04 '18 at 08:44

Java error: incompatible types: Object[] cannot be converted to Student[]

0 Answers0