CHS-J1 Cheat Sheet 2026: One-Page Review of Must-Know Facts

The Exam Snapshot: Facts You Must Know Cold

This page condenses CodeHS Java Level 1 (CHS-J1) into one reviewable sheet. It covers the exam mechanics first, then the five content domains, then the traps that cost candidates points. Everything here is drawn from the official CodeHS Java Level 1 Certification overview and the CodeHS Certifications FAQ. If you want the long-form version of any section, the CHS-J1 study guide walks through a full preparation plan.

Because CodeHS does not publish percentage weights for the five topic headings, you cannot safely skip any domain. Treat all five as live. The complete guide to the five content areas expands on how each heading breaks down.

Domain 1 Cheat Sheet: Java Fundamentals

This domain covers two named objectives: basic input and output using standard packages (including Scanner), and evaluating the scope of a variable. It is the smallest domain on paper, but the concepts underpin every code-reading question that follows.

Domain 2 Cheat Sheet: Data Types, Variables, and Expressions

This is the heaviest domain by number of named objectives: primitives with casting and arithmetic, Strings and string methods including parsing, arrays, ArrayLists, and 2D arrays. Expect a large share of the 45 questions to touch it, even though CodeHS does not publish an exact split.

Primitives, Casting, and Arithmetic

• Integer division truncates: 7 / 2 is 3, not 3.5. Dividing an int by an int never produces a fraction.
• Modulus returns the remainder: 7 % 2 is 1. It is the standard tool for even/odd checks and wraparound logic.
• Casting a double to an int truncates, it does not round: (int) 3.99 is 3.
• Cast placement matters: (double) (a / b) divides as integers first, then casts. (double) a / b casts first, then divides as doubles.
• Widening is automatic, narrowing needs a cast: assigning an int to a double is fine; the reverse is a compile error without an explicit cast.
• Know the common primitives: int, double, boolean, char.
• Compound assignment (+=, -=, *=) and increment/decrement (++, --) appear constantly inside traced code.

Strings and String Methods

• Strings are immutable. Methods like toUpperCase() return a new String; they do not change the original.
• Indexing starts at 0. length() returns the count of characters, so the last valid index is length() - 1.
• substring(start, end) includes start and excludes end. substring(start) runs to the end.
• indexOf(...) returns -1 when the target is not found.
• Compare Strings with equals(), not ==. Use compareTo() for ordering.
• Parsing means converting text to numbers, such as Integer.parseInt("42") and Double.parseDouble("3.5"). Know what kind of failure happens when the text is not numeric.

Arrays, ArrayLists, and 2D Arrays

Domain 3 Cheat Sheet: Flow Control

This domain covers Boolean expressions (understanding and evaluating logic) and iteration using for loops, for-each loops, and while loops.

Boolean Expressions

• Operators: && (and), || (or), ! (not), plus relational operators ==, !=, <, >, <=, >=.
• Short-circuit evaluation: in a && b, if a is false, b is never evaluated. In a || b, if a is true, b is skipped. This is how x != 0 && 10 / x > 1 avoids a divide-by-zero.
• De Morgan's laws: !(a && b) equals !a || !b, and !(a || b) equals !a && !b. Questions frequently ask which expression is equivalent to a negated compound condition.
• Precedence runs !, then &&, then ||. When in doubt, add parentheses mentally.
• A single = is assignment; == is comparison.

Loops

• A loop whose condition is false at the start runs zero times.
• Count iterations precisely: for (int i = 0; i < 5; i++) runs 5 times; for (int i = 1; i <= 5; i++) also runs 5 times.
• Nested loops multiply: an outer loop of 3 and an inner loop of 4 execute the inner body 12 times.
• A for-each loop cannot safely add or remove ArrayList elements during traversal.

Domain 4 Cheat Sheet: Object-Oriented Programming

This domain covers creating and using objects, writing classes (methods, instance variables, static methods), and recognizing class hierarchies and inheritance. The scope note matters: Level 1 excludes implementing inheritance, polymorphism, abstract classes, and interfaces. You must be able to read and recognize a hierarchy, but you are not being tested on building one. Do not spend your review time writing abstract classes or interface implementations; stay focused on what the exam covers.

Domain 5 Cheat Sheet: Recursion

The official topic is general recursion analysis, including understanding the base case and execution counts. This is an analysis domain: you read a recursive method and predict what it returns, how many times it runs, or why it fails.

• Every recursive method needs a base case that stops the recursion, and each recursive call must move toward it. A missing or unreachable base case leads to infinite recursion and a stack overflow.
• Trace from the top down, then resolve from the bottom up. Write each call, expand until the base case, then substitute return values back up the chain.
• Execution counts: count calls, not just the final answer. A method like f(n) that calls f(n - 1) once per call makes n + 1 calls when the base case is n == 0. A method that calls itself twice per call grows much faster.
• Order of statements matters: a print statement placed before the recursive call outputs in a different order than one placed after it. Questions love this distinction.
• Return versus print: know whether the method returns a value or prints as a side effect, and what each call hands back to its caller.

Classic Traps Hidden in Multiple-Choice Code Questions

With 45 multiple-choice questions, wrong answers are usually plausible results of a specific mistake. Recognizing the trap behind each distractor is a real scoring advantage. If you are weighing how demanding the test is overall, the CHS-J1 difficulty guide puts these patterns in context.

Scheduling Your Review Around the Five Domains

Since no domain weights are published, a balanced plan that front-loads the densest material works best. This sample sequence puts Domain 2 first because it contains the most named objectives and feeds every later topic.

Mixed timed practice is where you convert knowledge into exam speed. The CHS-J1 practice tests are built for exactly that kind of repetition, and you can review answers domain by domain afterward.

Vouchers, Attempts, and Credential Life

The administrative facts are short but worth memorizing so nothing surprises you on exam day.

• No prerequisites. CodeHS lists none, though it recommends the CodeHS AP CSA Course as preparation. The CHS-J1 requirements guide covers eligibility in more detail.
• A new voucher is needed for every attempt. If you do not pass, plan on obtaining another voucher before retesting rather than assuming a free retake.
• Credentials expire after 10 years. That is a long window, but it is a stated feature of the credential.
• Fees are not covered here. The official sources used for this sheet do not publish a fee, so check your school, district, or CodeHS contact for current pricing. The certification cost breakdown explains how costs are typically handled.
• Scheduling. For testing windows and deadlines, see the CHS-J1 exam dates page.

If you are still deciding whether the credential suits your goals, the ROI analysis weighs it against the effort required.

Frequently Asked Questions

Keep this sheet handy, trace every code snippet by hand, and take timed practice runs on the main practice test site until the two-minute-per-question pace feels natural.