Android app crashes when I create instance for a java class - firebase

Question

I was doing the update operation in Firebasae and im getting this error
here's the code
List<Student> studentsList;
mylistview.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
#Override
public boolean onItemLongClick(AdapterView<?> parent, View view,final int i, long id) {
Student students = studentsList.get(i);
showupdatedialogue(students.getName(),students.getName() );
return false;
}
});
Student students = studentsList.get(i); //line
App crashes on this line, "Student" is a java class
Student.java
package com.example.login;
import org.jetbrains.annotations.NotNull;
public class Student {
String name;
String roll_no;
String date_of_birth;
String class_section;
String class_teacher;
public Student(String name, String roll_no, String date_of_birth, String class_section, String class_teacher) {
this.name = name;
this.roll_no = roll_no;
this.date_of_birth = date_of_birth;
this.class_section = class_section;
this.class_teacher = class_teacher;
}
public String getName() {
return name;
}
public String getroll_no() {
return roll_no;
}
public String getdate_of_birth() {
return date_of_birth;
}
public String getclass_section() {
return class_section;
}
public String getclass_teacher() {
return class_teacher;
}
}
and I get this error, this says the size of the list is 0 but I have items in the list
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.login, PID: 18486
java.lang.IndexOutOfBoundsException: Index: 1, Size: 0
at java.util.ArrayList.get(ArrayList.java:437)
at com.example.login.MainActivity$5.onItemLongClick(MainActivity.java:111)
at android.widget.AbsListView.performLongPress(AbsListView.java:3291)
at android.widget.AbsListView$CheckForLongPress.run(AbsListView.java:3206)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
I/Process: Sending signal. PID: 18486 SIG: 9