Intro to Computer Science (Java) Study Guide
Six units for a first programming course, each topic linked to its own practice set. Each unit explains what to know, how to apply it, what typically goes wrong, and one study move that makes the material stick.
Six units
From first program through decisions, repetition, text, collections, and finally writing your own classes.
No exam
This is a first course. Assessment is by projects and quizzes rather than a national exam.
No prerequisite
Suitable for a student who has never programmed. Middle school through early high school is typical.
Where it leads
AP Computer Science A, which revisits every one of these topics at exam depth.
Units
Unit 1 is the largest by a wide margin. The rest move faster, and the last one is the bridge into calculus.
Unit 1 · Take your time
Storing values and doing arithmetic with them. Java asks you to say what kind of value each variable holds, which feels like extra work for about a week and then starts catching your mistakes for you.
Unit 2 · Steady
Teaching a program to choose. The syntax is short; the difficulty is writing conditions that are true exactly when you meant them to be, especially at the edges of a range.
Unit 3 · Heavy
Doing something many times without writing it many times. Most early loop bugs are off by exactly one, which is why counting the iterations deliberately matters more than the syntax.
Unit 4 · Steady
Text that you can look inside but never change. Counting from zero takes some getting used to, and almost every early text bug is a position being one off.
Unit 5 · Heavy
Holding many values under one name. Arrays are a fixed size; lists grow and shrink. This is also the first place two names can point at the same data, which surprises everyone the first time.
Unit 6 · Ends the course
Breaking a program into named pieces, then grouping data and behavior together into a class. This is the unit that makes larger programs possible rather than merely longer.
Mathematical Practices
Four habits that make a first programming course go well, practised from the first week rather than added later.
Write down what you expect the output to be, then run it. Being wrong is the useful part: the gap between prediction and result is exactly where the learning is, and running first hides it.
Keep a table with one column per variable and one row per line executed. This feels slow for three lines and becomes the only reliable method by ten.
Java errors name a type, a line, and usually a cause. An error is more informative than silently wrong output, which is why a strict language is easier to learn in than a permissive one.
When code misbehaves, change a single line and re-run. Changing three things and getting a different failure teaches nothing about which one mattered.
Assessment
Two lists: one for selected-response work, one for anything you have to write out.
Study plan
Four moves, in the order that pays off.
Predict output, be wrong, find out why. Students who run first and reason afterwards progress more slowly, even when their programs work.
Trace short programs by hand for the first few weeks. It is the skill every later unit assumes and the hardest one to add retroactively.
This one rule causes more confusion than anything else in the first term. Spend real time on it rather than working around it.
A small program you actually wanted teaches more than a longer exercise you were assigned. Pick something with an input, a decision, and a loop.
Splitting a working program into methods, while it still works, is the safest way to learn decomposition.
Types and boundaries feel abstract at the start and obvious once you are handling arrays. Re-reading early material later is not a step backwards.
Curriculum scope
The course teaches one skill from the first day: predict what the computer will do before you run it. Everything else is built on that. Java is strict about types and boundaries, and this guide treats that strictness as a teaching aid rather than an obstacle, because it turns vague mistakes into specific errors.
Essential foundations
Included in this sequence
Compare with the school syllabus
Glossary
Variable
A named place that holds one value.
Type
The kind of value a variable holds, such as a whole number, a decimal, or true-or-false.
Whole-number division
Dividing two whole numbers, which cuts off the remainder rather than rounding.
Cast
Telling Java to treat a value as a different type.
Boundary
The exact value at the edge of a range, where most mistakes happen.
Iteration
One pass through the body of a loop.
Running total
A variable that builds up a result across the passes of a loop.
Index
The position of an item, counted from zero.
Method
A named block of code that can be given values and can hand one back.
Return
Handing a value back from a method to whatever called it.
