CSE110 Principles of Programming with Java Lecture 24: References Javier Gonzalez-Sanchez [email protected] javiergs.engineering.asu.edu | javiergs.com Office Hours: By appointment

References

Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 3 Assignment | Primitive Types • The act of assignment takes a copy of a value and stores it in a variable • For primitive types:

Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 4 References • An object reference variable holds the memory address of an object • Rather than dealing with arbitrary addresses, we often depict a reference graphically as a “pointer” to an object • For object references, assignment copies the memory location: jane john jane john

Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 5 Assignment | References

Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 6 Arrays

Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 7 Assignment | References

Arrays of Objects

Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 9 Arrays of Objects • The elements of an array can be object references. • Suppose that we have the Student class Student[] list = new Student[5]; //The following causes NullPointerException int id = list[0].getID(); //We need to instantiate each object first: list[0] = new Student(“Bob”); list[1] = new Student(“Mary”); list[2] = new Student(“Peter”); // ... // OR we can use the Initializer: Student[] list = {new Student(“Bob”), new Student(“Mary”), new Student(“Peter”) };

Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 10 Arrays of Objects

Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 11 Arrays of Objects

Javier Gonzalez-Sanchez | CSE110 | Summer 2020 | 12 Reference Chapter 6

CSE110 - Principles of Programming Javier Gonzalez-Sanchez [email protected] Summer 2020 Disclaimer. These slides can only be used as study material for the class CSE110 at ASU. They cannot be distributed or used for another purpose.