mini exam 2

exception

an event that occurs during the execution of a program that encounters an error or some kind of exceptional situation

when do exceptions happen?

at runtime

exceptions should be _______ instead of _______

handled, avoided

when an exception occurs, two things happen (1)

an exception object is created and thrown

when an exception occurs, two things happen (2)

the normal flow of control is disrupted

stack trace

tells the user which methods were active when the program crashed

propogated

when the exception object is thrown/passed back to its calling method

try block

code that can thrown an exception

catch block

code for how you want to deal with the exception

unchecked exceptions

do not have to be caught; compiler will not generate an error message, but if there is a problem the program will crash at runtime

unchecked exceptions (ex:)

ArithmeticException, NullPointerException, NumberFormatException, StringIndexOutOfBoundsExceptionh

checked exception

must be caught or explicity propagated to the calling method; an error message at compile time

java.lang.RuntimeException

ensures an unchecked exception

throw keyword

is used to explicitly throw an exception

throws keyword

used to indicate that a method might throw a checked exception and propagate it

role of the interface

to define the set of behaviors (methods) that all of the implementing classes must contain

what is the goal of the interface?

to define the methods that each class must contain

contract

the interface is the _______ that each implementing class must follow

implementing classes

combining the interface with regular classes that provide implementations for the abstract methods

implements keyword

used by a class to implement an interface

inheritance

a way to create a new class based on an existing class without the need to manually copy-paste the source code

parent class, super class, base class

the original class you want to extend

child class, subclass, derived class

the new class you want to create based on the parent class

class hierarchy

a collection of classes related by inheritance

extends keyword

is used in the same class declaration of a child class to set up the inheritance relationship

java.lang.Object

superclass of all other classes

super keyword

how a child constructor can call the parent’s constructor on the first line of the child constructor

abstract methods

a non static (instance) method without an implementation (body)

constants

variables that are declared using the final keyword

-

private

~

package private

#

protected

+

public