A class is a template, or a blueprint, from which Java objects are created. All Java programs start with a class.
An object is a single instance of a Java class. An object has both state and behavior.
Programming model that focuses on **objects** and the data and actions associated with the objects.
The state of an object is all of the object's associated data. It is the *state* that the object is in.
The behavior of an object is what the object is able to do. It is the actions that can be performed by the object.
Instance is what you call a specific object constructed from a class. Instance and object generally refer to the same thing. An object is a specific instance of a class.
When someone else creates a Class (like `String`, or `Randomizer`), and you are using the functionality of that Class in your program, your program is a *client* of the class. You are using the class as a client.
A method is a way to teach the computer a new command
String is a Java type that represents a string of characters (text)
A variable defined in a Class, for which each object of the class has its own copy.
A constructor is a special method of a Class that constructs a new object (a new instance) of the Class and sets the initial values for the instance variables.
toString is a special method you write in your class that returns a String representation of the object.
A variable that receives a value passed into a method from outside the method.
A method's return type is the type of value returned from that method.
A method's signature is the name of the method and the parameter list.
An instance method is a method that defines the behavior of an object. It defines an action that the object can perform.
Visibility (usually `public` or `private`) defines who has access to something (usually a variable or method). Public means code outside of the class can access, private means only code inside the class can access.
A method called on the Class, rather than on a specific object of the Class.
A variable or attribute of a class that is shared between **all** instance of a class. Each instance **does not** get their own copy.
Related classes are grouped together into packages.
The `this` keyword is a reference to the current object (the current instance).
Class hierarchy refers to the arrangement of classes and how they relate to each other.
When a subclass extends a superclass, the subclass inherits all of the static methods, static variables, and public instance methods of the superclass. This is called inheritance.
A class, usually at the top of a Class Hierarchy, that cannot be instantiated, because not all of its methods are defined.
A method, written in an Abstract Class, that is not defined. The word `abstract` must come right before the method's return type. It is up to the subclass to fill in the definition for the abstract method.
The part of the method that contains the commands
If a subclass defines a new method body for a method defined in the superclass, then the subclass has **overridden** the method of the superclass.
An interface provides a list of methods that *must* be defined if a class chooses to implement the interface.
The Comparable Interface is a standard interface in Java that mandates that all classes implementing the Comparable interface must define a method called `int compareTo(Object o)` that returns a positive int if the parameter `o` passed in is *less than* the current instance, returns 0 if it is equal, and a negative int if it is greater.
Polymorphism is the capability of a method to do different things depending on which object it is acting upon.
Also called late binding, this refers to Java choosing the proper method to call at run time, as opposed to at compile time.
If a class A extends the class B, then A is a subclass of B.
If a class A extends the class B, then B is the superclass of A.
The `super` keyword lets us reference the superclass when writing code inside of a subclass.
A variable that is restricted to use in a certain scope of a program
Primitive types are the basic, simple data types that are inherent to Java (int, double, char, and boolean)
An instance method that allows the client to **get** the value of an instance variable on an object.
An instance method that allows the client to **set** the value of an instance variable on an object.
Classes can have multiple methods with the same name, as long as the parameters to those methods are different. Doing this is called "overloading" a method.
If two variables have the same name, and exist inside of the same scope, the variable with the *more specific* scope takes precedence. This is called shadowing. Local variables and parameters shadow the more general global variables (instance variables).
A symbol or container that holds a value.
When an object is assigned to a variable, the variable doesn't hold all of the object's data, it only holds a *pointer* to the object's data. The variable holds a memory location (think of it as a pointer to that memory location), and the object data is stored at that memory location.
Before an object variable is initialized, it doesn't point to any memory. It holds a **null pointer**.
Association for Computing Machinery: organization for computing professionals to provide guidance related to ethics and responsibilities.
When all programs and code will work as intended.
Prejudice in favor of or against one thing, person, or group compared with another, usually in a way considered to be unfair.
These classes are part of the java.lang package and Object class and have a number of useful methods.
Constructs a new Integer object or a new Double Object that represents the specified int or double value
The minimum/maximum value represented by an int or Integer, which are -2147483648 and 2147483647
Returns the value of this Integer as an int and this Double as a double
Automatic conversion between primitive types and their corresponding object wrapper classes
Reverse of autoboxing; automatic conversion from the wrapper class to the primitive type
The Object class is the superclass of all other classes in Java.
a way to create complex objects by combining simpler objects together, representing a “has-a” relationship between objects
