AP CSA Study Flashcards

Questions and Answers

What are parameters?

Inputs to a method (correct)

Outputs of a method

Variables within a class

None of the above

What is the method signature?

The name of the method and parameter list.

What is Javadoc?

A specific standard for commenting Java programs.

Strings in Java are mutable.

False Signup and view all the answers

Which of the following is a compile time error?

Missing a semicolon Signup and view all the answers

What will happen if you call a method on a null object?

A NullPointerException will be thrown. Signup and view all the answers

What is method overloading?

Multiple methods in a class with the same name but different parameters Signup and view all the answers

What does 'this' keyword refer to?

A reference to the current object. Signup and view all the answers

Match the following error types with their descriptions:

Compile Time Error = Errors in compiling Run Time Error = Error during program execution NullPointerException = Trying to use an uninitialized object ArithmeticException = Dividing by zero Signup and view all the answers

What happens when primitives are passed as parameters?

The primitive's data is copied, and the original remains unchanged. Signup and view all the answers

What is the purpose of a constructor?

To set initial values of instance variables. Signup and view all the answers

What is a class variable?

A variable that is common to all instances Signup and view all the answers

How do you create an Array in Java?

Type[] arrayName = new Type[numElements]; Signup and view all the answers

Study Notes

Parameters and Method Calls

Parameters act as inputs for methods, allowing data to be passed in.
Method calls follow the syntax: methodName(parameter, parameter);.
The style of invoking a method can involve user input, illustrated by echoing a string with parameters.

Method Return Types

The method return type indicates what type of value will be returned (e.g., int, double, String, or void).
For methods without a return value, use void, while return types determine the data type of the return value.

Method Signature and Javadoc

A method signature includes the name and parameter list, such as private int square(int x);.
Javadoc is a standardized commenting method for Java programs, starting with a comment format before the method declaration.

String Properties and Manipulations

Strings are objects representing sequences of characters, indexed starting from 0 and are immutable (unchangeable).
Use the ‘+’ operator to concatenate strings, forming new strings in the process.

Error Types and Common Exceptions

Compile Time Errors occur during compilation due to syntax issues, while Run Time Errors appear during program execution, such as division by zero.
Common exceptions include ArithmeticException, IndexOutOfBoundsException, and NullPointerException, each indicating specific programming errors.

Object-Oriented Concepts

Objects contain state (data) and behavior (methods) and are instances of classes.
Classes serve as templates for creating objects, defining their common behaviors and properties.
Instance variables hold the state for each object, with each instance of a class having its unique data attributes.

Constructors and Methods

Constructors initialize objects and set instance variable values, specified with matching parameters.
Instance methods define the behavior of objects and can access instance variables.

Accessor and Modifier Methods

Getter methods allow access to instance variables, while Setter methods modify their values, following naming conventions for clarity.

Static Class Components

Static variables and methods belong to the class as a whole rather than to instances, allowing shared access without creating objects.

Method Overloading and Variable Scope

Method overloading allows multiple methods to share the same name but requires differing parameter types, numbers, or orders.
Variable scope defines the visibility of variables, existing from their declaration until the end of the block.

Java Packages and Visibility

Packages group related classes, and can be imported either entirely or selectively.
Visibility modifiers control access: Public allows access anywhere, and Private restricts it to within the defining class.

The `this` Keyword and Object References

The this keyword refers to the current object, resolving naming conflicts and clarifying instance variable references.
Objects in memory are referenced by pointers, requiring methods like .equals() for value comparison instead of == which compares memory locations.

Primitives and Objects as Parameters

Passing primitives to methods copies their data, leaving the original unchanged.
Passing objects allows changes to the parameter to affect the original object due to shared references.

NullPointerException and Abstract Classes

A NullPointerException arises when methods are invoked on uninitialized object references.
Abstract classes cannot be instantiated and may contain abstract methods that subclasses must implement.

Data Structures in Java

Common data structures include Arrays, ArrayLists, and HashMaps, each organizing data in unique ways.
Arrays hold fixed numbers of elements of the same type, and ArrayLists automatically resize, offering additional methods for manipulation.

Working with Arrays

Arrays are created through the syntax Type[] arrayName = new Type[numElements]; and support accessing and modifying values via indices.
Use arrayName.length to retrieve the total number of elements, with iteration achieved through loops.

ArrayList Functionality

ArrayLists can dynamically resize and easily manipulate elements, making them versatile for handling collections.

Description

Test your understanding of key concepts in AP Computer Science A with these flashcards. Cover essential topics such as parameters, method calls, and return types. Perfect for quick reviews and exam preparation.