Advanced Placement�Computer Science A�(Java)

Mr. (Raymond) Chan

Lowell High School

San Francisco, CA

Welcome!

Find your assigned seat.

“Last Name, First Name Initial”

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This classroom is nut free

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AP Computer Science A (Java) is an advanced computer science course equivalent to a first semester college class such as 111B Programming Fundamentals: Java at City College

Course Prerequisite: B or better in APCS Principles or Computer Programming A or equivalent

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Not sure if you have met the prerequisite? Ask you instructor!

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Equivalent to a half a semester of an introductory CS course, depends on the college

Course Requirements:

• Prior programming experience (Principles, CPA/B, self study)
• Use of Google Classroom and Synergy
• A Git Hub account to share your programs on the web

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Norms

• Stay home if you are not feeling well
• Respect others privacy and personal space
• Minimize eating or drinking in the classroom
• Wash your hands throughout the day
• Let me know if you need to leave the room
• Always sit in your assigned seat
• Not required, but feel free to wipe down the keyboard, mouse and desk
• Dress warm, we’ll keep the windows and door open to promote ventilation

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Lowell has a mouse problem

• You are welcome to eat in class, but. . .
• Please do not through away food or wrappers in the classroom
• Use the composting bins in the hallway

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What you’ll learn

• Advanced Java Programming
• Object Oriented Programming including inheritance
• How to make and maintain your own website
• How to write (a little) HTML & CSS
• How to use Git Hub
• Searching and sorting
• Recursion
• Good Programming Style
• All APCS A topics and a good foundation for studying computer science in college
• + Fun stuff like Asteroids that isn’t on the AP exam that they don't teach you in college!

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apcslowell.github.io

• The complete course is online at GitHub
• We’ll start at the top and work our way to the bottom

You are here

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Grading Policy

• Grades are cumulative and point based
• Points will be assigned for

tests and quizzes

programming assignments

weekly reflections

• All students are expect to take the AP CS A Exam is the afternoon of Friday, May 15, 2026

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Professionalism

• How you conduct yourself during your work
• Includes (but not limited to)
• Phone and Computer etiquette
• Reliability and accountability
• Ethics
• Working cooperatively and respectfully with your peers and teachers

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Weekly Reflections

• Answering the following questions:
• What did you learn the past few days?
• What did you accomplish the past few days?
• What mistake(s) did you make?
• What questions do you have?
• What do you want to learn more about?

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Weekly Reflections

• Good Example

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“Monday: Today I went over three practice questions and got most of them correct. I want to learn more about coding different shapes besides the ellipse, square, and triangle. Tuesday: Today I went over another practice quiz question and I answered it correctly. I found out that the mistake I made with one of the questions yesterday was I said that capitalization doesn't matter in code,when it actually does. Wednesday: Today I made a simple pen picture on code pen following the directions from the slides. However, I might've made a mistake with my animal project, because the background wouldn't show up even though I changed the color. Thursday: The mistake I made yesterday was that I forgot to add the p5.js library to my settings. Today I decided what animal I want to do but I couldn't get anything to show up on codepen besides the background. Friday: Today I finished my first programming quiz in around 20 minutes. I'm unsure about two or three answers that I chose, but overall I feel pretty good about the test.“

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Weekly Reflections

• Bad Example (I appreciate honesty tho)

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“I learned nothing. I also learned very little more. I accomplished nothing. I accomplished very little else.“

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“October 21-25 I'd either slept, on my phone watching YouTube videos, or did work for other classes which I didn't even finish or turn in (ik I'm smart :)). Since I didn't pay attention to any of last week's lectures and let my chromebook sleep for most of the class, I didn't conplete this Dice Game assignment nor any previous unfinished assignments.”

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“...Tuesday - I had a good breakfast, good day. Had some knowledgable moments in Physics. Wednesday - Learned how to eat properly again. Ate an apple from top to bottom… Friday: Found myself reminiscing whether to spoil Endgame for myself. Ended up not, going to watch it later tonight.”

• These students got half credit.

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Restroom policy

• Please ask!
• I need to know where you are
• Please do not leave the room during a quiz
• Sign on the clipboard by the door

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• Go to apcslowell.github.io and click the links to:
• Enter your contact info (you must sign in with your SFUSD username)
• Sign up for Piazza (It says Fall 2025)
• Join code apcsa

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• While you are doing all that, I’ll take roll
• Extra time? Browse apcslowell.github.io
• Any questions?

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• Go to apcslowell.github.io and click the links to:
• Enter your contact info (you must sign in with your SFUSD username)
• Sign up for Piazza
• Join code apcsa

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• While you are doing all that, I’ll take roll
• Extra time? Browse apcslowell.github.io
• Stuck? Consult next few slides
• Any questions?

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• Sign up for Piazza

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• http://piazza.com/lowell_high_school/fall2025/apcsa
• access code is apcsa
• when asked to join the “Piazza Network”, skip it.
• Click on the gear to change your email settings to your liking. Previous students disliked numerous emails they got.

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• All 2 sections of AP CS A will using Piazza
• Post your questions there
• You can respond and help each other here
• Send emails to your teacher for personal matters

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• Sign up for CSAwesome - SPOT THE DIFFERENCE

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• Sign up for CSAwesome - SPOT THE DIFFERENCE

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• Sign up for CSAwesome - SPOT THE DIFFERENCE
• Make sure you are signed in and in the correct course, ie “Lowell-CHAN-2020-21”

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• This ensures your progress is saved, so when I decided to grade your work, you will get points.

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Submitting your GitHub URL

• Sign in to GitHub and go to your profile

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• Copy the URL of your profile

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• Sign in to Google Classroom and find the Sign up for GitHub.com assignment. Choose Add | Link to submit the link to Google classroom

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Proceed with some caution.

Slides from this point forward are not updated for the 2022-23 year.

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Tutoring

• Office Hours/Tutoring Times:
• Mr. Simon can tutor students before school between 8 and 9 am, during blocks 3, 5, 7, 8 and after school between 2:10 and 2:40 pm.
• Mr. Chan can tutor any APCSA Java students during blocks 2, 3, 5, 8 and evenings 8-9pm
• Peer tutoring through CSF:
• appointments can be schedule at lowellcsf.weebly.com
• drop in tutoring in the library every school day from Block 1 to 4:45 PM after school
• Lowell’s after school computer science clubs:
• Girls Who Code
• Dev (App Development) club
• EECS (Electrical Engineering and Computer Science)

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Java Basics

• The common building blocks in programming languages are:
• Variables
• Loops
• if statements
• Functions (aka “methods”)
• It’s expected that you have done programming with these already in some language
• Over the next two weeks we’ll go over how these work in Java

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A basic Java “Hello World” program

• Click on the link to the “Four 4s Challenge” of just go to apcslowell.github.io/APJavaBasics/
• It might look complicated at first, but . . .

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A basic Java program

• It turns out that this line is much more important than the others
• So we can ignore everything except the code circled in green

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Statements

• The circled code is an example of a statement
• It’s like an English sentence
• A semi-colon marks the end of a Java statement

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String

• "Hello World!" is a Java String
• A String is a collection of letters, digits, punctuation and/or spaces
• The beginning and end of the String are marked with double quotes (")

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print() vs println()

• System.out.println() prints first and then goes to the next line

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print() vs println()

• System.out.print() prints, but it does NOT go to the next line
• If we change the first statement to System.out.print() "Bottom" is printed on the same line as "Top"

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print() vs println()

• Changing the second statement to System.out.print() doesn’t change the output since nothing is printed after "Bottom"

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Comments

• Lines that begins with two slashes // are ignored by Java

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• Comments have no effect on the execution of the program, but they make it easier for other programmers (and your future self) to understand what you meant to do

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Escape Sequences

• Special characters
• In Java, Escape Sequences begin with a backslash \
• A good way to remember the difference between a backslash and a forward slash is that a backslash leans backwards ( \ ), while a forward slash leans forward ( / )

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Common Java Escape Sequences

• \n Insert a newline in the text at this point

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Common Java Escape Sequences

• \t Insert a tab in the text at this point

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Common Java Escape Sequences

• \' Insert a single quote character
• \" Insert a double quote character
• \\ Insert a backslash character

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Formatting Java code

• In Java programs, some spaces are required
• For example, you need at least one space between keywords
• The program below is not legal

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Formatting Java code

• But most other spaces are optional
• For example, this program is legal but hard to read

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Formatting for easier reading

• The blank space (also called “white space”) commonly used to format code is:
• Indentation inside of { }
• One statement per line

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Debugging

• Errors in programs are called “bugs”
• The process of fixing program errors is called “debugging”
• It’s good to work around other programmers when you are learning a new programming language
• Asking for help with debugging is a part of learning

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Errors

• When you write Java programs you will often get an error message
• When you are learning a new programming language, errors are a fact of life
• Errors are ok, just fix them and move on

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Syntax error

• In this case I made a syntax error
• Syntax is the grammar and spelling of a computer language
• Here I forgot the double quotes around my name

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Logic error

• This time I misspelled my name
• The computer doesn’t know my name, so the program runs incorrectly without an error message

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(Run time) Exceptions

• Sometimes a logic error crashes the computer and stops the running program
• Here I made the logic error of dividing by zero

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Arithmetic in Java

+ - * /

• Addition
• Subtraction
• Multiplication
• Division

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Literals vs. Expressions

• Double quotes around text tells Java it is an expression
• Java will print an expression exactly as written

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Literals vs. Expressions

• Here’s an expression "4/4"
• Java prints it in exactly the same form

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Literals vs. Expressions

• Here’s an expression 4/4
• Java evaluates it to get an answer 1
• And then prints it

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Four 4s challenge

• Use exactly four 4's to write an expression that evaluates to every integer from 1 to 10, using only + - * / and ()
• No decimals, factorials, square roots, exponents, etc.

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Four 4s challenge

• Print 10 expressions that use arithmetic and four 4s that evaluate to 1 through 10
• Here’s one way to do the first

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