Only the last Object is added to the ArrayList

Question

I created a user defined data type and read data from a file. Here are the codes:

Student Class:

package system.data;

public class Student {

private St         


        

Answer 1

The same student object is reused, because Java passes a reference to an object in the call that adds the student to the list. In other words, the original student is passed each time. The solution is to create a new Student for each call.

for (String item : strList) {
    int x = 0;
    String[] arr = item.split(":");

    Student student = new Student();

    student.setFirstName(arr[0]);
    student.setLastName(arr[1]);
    student.setRegNumber(arr[2]);
    student.setCoursework1Marks(Integer.parseInt(arr[3]));
    student.setCoursework2Marks(Integer.parseInt(arr[4]));
    student.setFinalExamMarks(Integer.parseInt(arr[5]));

    studentDetails.add(student);
}

Answer 2

try moving Student student = new Student(); inside the for loop:

 for (String item : strList) {
    int x = 0;
    String[] arr = item.split(":");
    Student student = new Student();
    student.setFirstName(arr[0]);
    student.setLastName(arr[1]);
    student.setRegNumber(arr[2]);
    student.setCoursework1Marks(Integer.parseInt(arr[3]));
    student.setCoursework2Marks(Integer.parseInt(arr[4]));
    student.setFinalExamMarks(Integer.parseInt(arr[5]));

    studentDetails.add(student);
}

hope this helps.

Answer 3

create new instance of Student object inside the for loop

like this

for (String item : strList) {
        int x = 0;
        String[] arr = item.split(":");
        Student student = new Student();
        student.setFirstName(arr[0]);
        student.setLastName(arr[1]);
        student.setRegNumber(arr[2]);
        student.setCoursework1Marks(Integer.parseInt(arr[3]));
        student.setCoursework2Marks(Integer.parseInt(arr[4]));
        student.setFinalExamMarks(Integer.parseInt(arr[5]));

        studentDetails.add(student);
    }

Answer 4

Actually you are always using the same student object.You have to put Student student = new Student(); inside the for loop.