AP Computer Science A Unit 3 Cheatsheet: Class Creation

Abstraction: Reducing complexity by hiding irrelevant details and focusing on main ideas.

• Data abstraction: Separates abstract properties from concrete representation; gives data a name without exposing implementation details.
• Procedural abstraction: Names a process; method can be used knowing what it does, not how.
• Method decomposition: Break large behaviors into smaller methods to enable code reuse and manage complexity.
• Parameters: Generalize procedures so they work with a range of input values.

Design first: Plan classes (attributes + behaviors) using natural language or diagrams before coding.

this: Special variable in instance methods/constructors that holds reference to current object.

• Use to disambiguate: this.instanceVar vs. local variable
• Pass current object as argument: method(this)
• Call another constructor: this(...)

Class methods: Do not have this reference (no current object).

System reliability: Program performs tasks as expected under stated conditions without failure. Test with variety of conditions.

Program impact: Computing systems affect society, economy, and culture—both beneficial and harmful. Unintended consequences possible.

Intellectual property:

• Open source: Free to use, modify, and share only if you follow its license terms
• Proprietary code: Requires permission and often payment before integration

Programmer responsibility: Consider reliability, unintended harms, and legal/ethical code reuse.