---
title: "Behavior — AP Computer Science A Definition & Exam Guide"
description: "In AP CSA, behavior is what an object can do, defined by its class's methods. Pairs with attributes (data) and shows up in class design FRQs and API reading."
canonical: "https://fiveable.me/ap-comp-sci-a/key-terms/behavior"
type: "key-term"
subject: "AP Computer Science A"
unit: "Unit 1"
---

# Behavior — AP Computer Science A Definition & Exam Guide

## Definition

In AP Computer Science A, a behavior is what instances of a class can do, or what can be done with them, and it is defined by the class's methods. Behaviors pair with attributes (the data stored in instance variables) to make up the blueprint a class provides for its objects.

## What It Is

A behavior is the "action" half of a [class](/ap-comp-sci-a/unit-3/abstraction-and-program-design/study-guide/o9VgVeIpKRYZ7N7rXfUz "fv-autolink"). Per the CED, [attributes](/ap-comp-sci-a/key-terms/attribute "fv-autolink") are the data related to a class (stored in variables), while behaviors refer to what instances of a class can do, or what can be done with them, and they're defined by methods (EK 1.7.A.2). When you call `myAccount.deposit(50.0)` or `str.substring(0, 3)`, you're invoking a behavior.

Think of a class as a blueprint with two columns. One column lists what every object *has* (attributes like a `balance` or a `title`), and the other lists what every object *can do* (behaviors like `deposit` or `checkOut`). A class is the formal implementation of both the attributes and behaviors of an object (EK 1.12.A.1), so when you create an object, it comes with all the behaviors its class defined. You don't have to see the method's code to use a behavior, either. [API documentation](/ap-comp-sci-a/unit-1/documentation-with-comments/study-guide/scrDad77j4e5vwrFab5J "fv-autolink") tells you what a class's behaviors are and how to call them, which is exactly how you use library classes like `String` and `Math` without ever reading their source.

## Why It Matters

Behavior is one of the core vocabulary words the CED uses to describe object-oriented programming, and it threads through both [Unit 1](/ap-comp-sci-a/unit-1 "fv-autolink") and Unit 3. In Topic 1.7, LO 1.7.A asks you to identify the attributes and behaviors of a class found in API [libraries](/ap-comp-sci-a/key-terms/library "fv-autolink"), so reading documentation and spotting "here's what this object can do" is literally a learning objective. In Topic 1.12, LO 1.12.A asks you to explain the class-object relationship, and that explanation hinges on the blueprint defining attributes and behaviors. Then in Unit 3, the perspective flips. Instead of using behaviors someone else wrote, you write them yourself as methods, and LO 3.3.A adds access control, deciding whether a behavior is `public` (callable from outside) or `private` (an internal helper). If you can't name the difference between an attribute and a behavior, Unit 3 class design will feel like guesswork.

## Connections

### [Attribute (Units 1 & 3)](/ap-comp-sci-a/key-terms/attribute)

Attributes and behaviors are the two halves of every class. Attributes are the data an [object](/ap-comp-sci-a/key-terms/object "fv-autolink") stores in variables, and behaviors are the methods that act on that data. A `BankAccount`'s `balance` is an attribute; `deposit` is a behavior that changes it.

### Library and API Documentation (Unit 1)

API specs exist to tell you a class's attributes and behaviors without showing you the code. Reading a [method signature](/ap-comp-sci-a/key-terms/method-signature "fv-autolink") in documentation is reading a behavior's contract, which is how you use `String` or `Math` methods correctly on the exam.

### Inheritance and Class Hierarchies (Units 1 & 3)

Per EK 1.12.A.2, common behaviors of related classes get pulled up into a [superclass](/ap-comp-sci-a/unit-1/objects-instances-of-classes/study-guide/EcpFHGcIKu6385hMohLe "fv-autolink"), and subclasses inherit them without rewriting the code. Inheritance is basically behavior reuse organized as a family tree.

### Data Encapsulation (Unit 3)

Encapsulation hides an object's attributes behind `private` and exposes carefully chosen `public` behaviors instead. Outside code never touches `balance` directly; it asks the object to `deposit` or `withdraw`. Behaviors become the only doorway into the data.

## On the AP Exam

You won't get a question that just says "define behavior," but the concept is everywhere. Multiple-choice questions ask you to describe the class-object relationship, and the correct answer almost always uses the blueprint language of attributes and behaviors (a class defines them; an object is one specific instance with them). Design-flavored MCQs, like modeling a `Book` that can be checked out or returned, test whether you can sort a description into attributes (title, author, ISBN) versus behaviors (checkOut, return). On the FRQ side, Question 1 (Methods and Control Structures) and the class design question are entirely about implementing behaviors as methods. The 2018 FRQ with the `StringChecker` interface and the 2026 FRQ with the `Space` class's `getColor` method both hand you a behavior's contract (the method header and comment) and ask you to write or use code that fulfills it. Your job is to read a behavior's specification and either implement it or call it correctly.

## behavior vs attribute

Attributes are what an object HAS; behaviors are what an object DOES. Attributes are data stored in variables (like `balance` or `title`), while behaviors are defined by methods (like `deposit` or `checkOut`). Quick test: if it's a noun describing the object's state, it's an attribute. If it's a verb describing an action, it's a behavior. Exam questions about class design often hinge on sorting a scenario's details into these two buckets.

## Key Takeaways

- A behavior is what instances of a class can do, or what can be done with them, and behaviors are always defined by methods.
- Attributes are the data half of a class (stored in variables) and behaviors are the action half (defined by methods), and the CED treats these as the two pieces every class blueprint contains.
- You can use a behavior without seeing its code because API documentation describes each class's attributes and behaviors, which is how you call methods on library classes like String.
- Subclasses inherit the behaviors of their superclass, so common behaviors get written once in the superclass and reused down the hierarchy.
- In Unit 3, you control who can use a behavior with access modifiers, where public methods are callable from outside the class and private methods are internal helpers.

## FAQs

### What is a behavior in AP Computer Science A?

A behavior is what instances of a class can do, or what can be done with them, and it is defined by the class's methods. For example, `deposit` and `withdraw` are behaviors of a `BankAccount` class.

### What's the difference between a behavior and an attribute?

Attributes are an object's data, stored in variables (like a `balance`), while behaviors are an object's actions, defined by methods (like `deposit`). Per EK 1.7.A.2, this attribute/behavior split is how the CED describes every class.

### Are behaviors and methods the same thing?

Almost. A behavior is the concept (what an object can do) and a method is the Java code that implements it. On the exam the terms are used nearly interchangeably, because every behavior in your code is a method.

### Do objects of the same class have the same behaviors?

Yes. Every object of a class gets all the behaviors the class defines, because the class is the blueprint (EK 1.12.A.1). What differs between objects is their attribute values, like two `BankAccount` objects with different balances, not which methods they can run.

### Can a behavior be private in Java?

Yes. A `private` method is a behavior only the declaring class can use, typically a helper method. The behaviors meant for outside code are marked `public`, which is the core of encapsulation in Topic 3.3 (LO 3.3.A).

## Related Study Guides

- [1.7 Application Program Interface (API) and Libraries](/ap-comp-sci-a/unit-1/application-program-interface-api-and-libraries/study-guide/sEpH1rg9TzREJwynSE9N)

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