Untitled Flashcards Set

clone()

Creates and returns a copy of this object (protected method return: Object).

equals(Object obj)

Indicates whether some other object is 'equal to' this one (return: boolean).

hashCode()

Returns a hash code value for the object (return: int).

toString()

Returns a string representation of the object (return: String).

Class

A class defines a type and is used to define what all objects of that class know and can do.

Compiler

Software that translates the Java source code (ends in .java) into the Java class file (ends in .class).

Compile time error

An error that is found during the compilation, also known as a syntax error.

Constructor

Used to initialize fields in a newly created object.

Field

A field holds data or a property—what an object knows or keeps track of.

Java

A programming language that you can use to tell a computer what to do.

Main Method

Where execution starts in a Java program.

Method

Defines behavior—what an object can do.

Object

An instance of a class with defined attributes. Objects are declared as variables of a class type.

Syntax Error

An error in the specification of the program.

Instance Variable

Variables that belong to an object (instance of a class).

Local Variables

Variables that are declared inside of methods and constructors, only accessible within those blocks.

Constructors

Initialize the attributes in newly created objects—they have the same name as the class.

Signatures

The unique combination of both name and formal parameters for a method or constructor.

Modifiers

Modifiers (e.g., public, private, protected, final, static) define the behavior, accessibility, and scope of classes, methods, and variables.

Overloading

When there is more than one constructor, differing in the number, type, or order of parameters.

Overriding

Occurs when a subclass implements a method already defined in the superclass.

Default constructor

A constructor that doesn’t take any parameters.

Parameters

Allow values to be passed to the constructor to initialize newly created object’s attributes.

Parameter list

A list of the type of the value being passed and a variable name in the header of a constructor or method.

Actual parameters

The values being passed to a constructor or method.

Formal parameters

Specified variables in the header of a constructor/method that act as placeholders for actual parameters.

Call by value

When you pass a value, it passes a copy of the value of the actual parameters.

Dot operator

Used to access member methods and variables of a class or an instance of that class.

Procedural abstraction

Allows a programmer to use a method by knowing in general what it does without knowing how it does it.

NullPointerException

Occurs if you try to call an object method on an object variable whose value is null.

Object method

A non-static method belonging to an object or a particular instance of the class.

Static method

Belongs to the class and not to a particular instance of the class.

Data encapsulation

Where the data and the code acting on the data are wrapped together into a single unit.

Getters/Setters

Public methods in a class used to return or set private instance/class variables.

class

The class keyword is used to define a new class.

public

A visibility keyword that allows direct access from any class.

private

A visibility keyword that restricts access to only the current class.

new

A keyword used to create a new object of a class.

static

Designates that a class member belongs to the class and not a single object.

final

Indicates that a variable, method, or class cannot be modified or extended.

return

The keyword that finishes the execution of a method and can return a value.

void

Specifies that a method should not have a return value.