Object Reference Assignment

Refer to the following class:

public class Student 
{
    private String name;
    private double gpa;

    public Student(String newName, double newGPA) 
    {
        name = newName;
        gpa = newGpa;
    }

    public String getName() 
    {
        return name;
    }
    /* Additional methods not shown */
}

Consider the following code segment.
Student s1 = new Student("Brody Kai", 3.9);
Student s2 = new Student("Charlie Cole", 3.2);
s2 = s1;
s2.setGpa(4.0);
System.out.println(s1.getGpa());

What is printed as a result of executing the code segment?