Why am I getting null pointer exception in this program when using enhanced for loop

I am getting a null pointer exception in the selectAllStudent Method. When I am using foreach loop but When I am using a normal loop it is working fine. Please explain the reason. Thank you

Driver Class

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Test {

    public static void main(String[] args) {
        Student[] sdb = new Student[2];
        try {
            for (Student s : sdb) {
                s = takeInput();
            }
        } catch (IOException ioe) {
            System.err.println(ioe.getMessage());
        }
        selectAllStudent(sdb);
    }

    static void selectAllStudent(Student[] sdb) {
        for (Student s : sdb) {
            s.printStudentDetails();               // Getting NullPOinterException here
        }
    }
    public static Student takeInput() throws IOException{
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter the details ");
        System.out.print("ROLL      :"); int rollno = Integer.parseInt(in.readLine());
        System.out.print("NAME      :"); String name = in.readLine();
        System.out.print("BRANCH    :"); String branch = in.readLine();
        return (new Student(rollno,name,branch));
    }  
}

Student Class

public class Student {

    private int rollno;
    private String name;
    private String branch;

    Student(int rollno, String name, String branch) {
        this.rollno = rollno;
        this.name = name;
        this.branch = branch;
    }

    void printStudentDetails() {
        System.out.println("ROLLNO  :" + rollno);
        System.out.println("NAME    :" + name);
        System.out.println("BRANCH  :" + branch);
        System.out.println("-------------------");
    }
}