Final Exam

Question 1

INHERITANCE

Answer 1

REDUCES PROGRAM DEVELOPMENT TIME

Object-oriented programming allows classes to inherit commonly used state and behavior from other classes. In this example, Bicycle now becomes the superclass of MountainBike, RoadBike, and TandemBike. In the Java programming language, each class is allowed to have one direct superclass, and each superclass has the potential for an unlimited number of subclasses

class MountainBike extends Bicycle {

    // new fields and methods defining
     // a mountain bike would go here

}

Question 2

The direct superclass of a subclass (specified by the keyword extends in the first line of a class declaration) is the superclass from which the subclass inherits. An indirect superclass of a subclass is two or more levels up the class hierarchy from the subclass.

Answer 2

Superclass Subclass

Shape Circle, Triangle, Cube

Student UndergradStuedent

Employee Faculty, Staff

Question 3

Single Inheritance

Answer 3

A class is derived from one direct superclass. In multiple inheritances a class is derived from more than one direct superclass.

Java does not support multiple inheritance

Question 4

Subclass

Answer 4

is more specific than its superclass and represents a smaller group of objects

Every object of a subclass is also an object of that class’s superclass.

However a superclass object is NOT an object of its class’s subclass

Question 5

is-a relationship

Answer 5

Represents inheritance

A object of a subclass also can be treated as an object of its superclass

Ex: Vehicle, represents all vehicles, cars, trucks, boats, bicycles etc…..

**public class Animal**{
 }

public class Mammal extends **Animal{**
 }

public class Reptile extends **Animal**{
 }

public class Dog extends **lMamma**{
 }

Question 6

A Has-a relationship

Answer 6

Represents composition,

A class object contains refrences to objects of other classes

Ex: A car has a, steering wheel

Question 7

Superclasses and Subclasses

Answer 7

Single inheritance relationships form treelike hierarchial structures,

a superclass exists in a hierarchical relationship with its subclass

Question 8

Protected Members

Answer 8

A superclass’s public memebers are accessible whereever the program has a reference to an object of that superclass or one of its subclass

A superclass’s private members can be accessed directly only within the superclass’s declaration

A superclass’s protected members have an intermediate level of protection btw public and private access. They can be accessed by memebers of its subclass, and by members of other classes in the SAME package

Superclass’s private members are hidden in its subclasses and can be accessed only through the public or protected methods inherited from the superclass\

Overridden canbe accessed by a super and a dot(.) seperator.

Question 9

Relationship btw Superclass and Subclasses

Answer 9

Subclass CANNOT access the private members of its superclass, but CAN access the non-private members

Subclass, can invoke a constructor of its superclass by using the keyword “super” followed by parathensis with superclass arguments. Must appear in the first statement of the subclass constructor body

Question 10

_______ is a form of software reusability in which new classes acquire the members of existing classes and embellish those classes with new capabilities

Answer 10

Inheritance

Question 11

A superclass’s _____ members can be accessed in the superclass declaration and in subclass declarations.

Answer 11

Public and Protected

Question 12

In a ______ relationship, an object of a subclass can also be treated as an object of its superclass.

Answer 12

is-a or inheritance

Question 13

In a _____ relationship, a class object has references to objects of other classes as members

Answer 13

has-a or composition

Question 14

In a single inheritance, a class exists in a ____ relationship with its subclasses

Answer 14

hierarchical

Question 15

A superclasses _____ members are accessible anywhere that the program has a reference to an object of that superclass or to an object of one of its subclasses

Answer 15

Public

Question 16

When a object of a subclass is instantiated a superclass ______ is called implicityly or explicityly.

Answer 16

constructor

Question 17

Subclass constructors can call superclass constructors via the ______ keyword

Answer 17

super

Question 18

Polymorphism

Answer 18

Enables us to write programs that process objects that share the same superclass as if they’re all objects of the superclass

Can simplify programming

We can design and implement systems that are easily extensible. The only parts of a program that must be altered to accomadate new classes are those that require direct knowlege of the new classes that you add to the hierarchy.

Question 19

If a class contains at least one abstract method, its an_____ object

Answer 19

Abstract

may or may not include abstract methods. Abstract classes cannot be instantiated, but they can be subclassed.

public abstract class GraphicObject {
    // declare fields
    // declare non-abstract methods
    abstract void draw();
 }

Question 20

Classes from which objects can be instantiated are called _____ classes

Answer 20

Concrete

Question 21

_____ involves using a superclass variable to invoke methods on superclass and subclass objects, enabling you to “program in the general”

Answer 21

Polymorphism

Question 22

Methods that are not interface methods and that do not provide implementations must be declared using the keyword _____

Answer 22

abstract

Question 23

Casting a reference stored in a superclass variable to a subclass type is called _______

Answer 23

downcasting

Question 24

Abstract Class

Answer 24

can include methods with implementations and abstract methods

Question 25

Trying to invoke a ***subclass-only method*** with a superclass variable

Answer 25

Is NOT allowed

Question 26

Only a **concrete subclass**

Answer 26

**MUST** implement the method

Question 27

**_Encapsulation_**

Answer 27

Classes encapsulate attributes and mehods into objects, which are intimately related ***Implementation details are hidden within the objects thenmselves*** \*Hiding the the complexity of the code \*Hide data \*Variables and Methods or Programs \*Private or Public

Question 28

\*Java IS case sensitve

Answer 28

- Standards, should tag several words to be descriptive (**Lowercase, WITHOUT spaces, first word after the first word starts with a uppercase letter**) keywords are always written in lowercase Always make sure the class name in your code and java filename match. - Never name with a # first

Question 29

3 control structures in every program language and can be applied to Java

Answer 29

+ Always in default is "**sequential**" + Other 2 are exceptions to the standard "sequential" which is "**selection**" and "**repitition**" The IF statement lets you execute a sequence of statements conditionally ** IF-THEN, IF-THEN-ELSE, and IF-THEN-ELSIF** **IF sales \> quota THEN** compute\_bonus(empid); UPDATE payroll SET pay = pay + bonus WHERE empno = emp\_id; END IF; **\* Biggest mistake is not allowing an EXIT to occur**

Question 30

\* IF PROGRAM LOCKS UP

Answer 30

it is in a indefinite loop + This is because the program didn't assign variable in the repeat loop

Question 31

Categories of Repeat Loops (Logic Bases) what you want to do in the repeat loop

Answer 31

+ Entrance Control Loops **while** (test) { body-statements; } // while next-statement; **_ Do loops have the form_** **do** { body-statements; } while (test); next-statement; **for** (initialization; test; increment) { body-statements; } // for + Exit Control Loops

Question 32

Lets say the Loop is using a lot of Arrays

Answer 32

+ to help index the Arrays you can use a ***counter loop *** int x = 0; **while (x \< 5)** { printf ("x = %d\n", x); x++; } + if you have a Array of integers you can use a "***value statement"*** int month = 8; **if (month == 1)** { System.out.println("January"); } else if (month == 2) { System.out.println("February"); } ... // and so on + Array of strings, fastest way to intialize that would be address the array by its apparent name

Question 33

No subscript on Variable...how does Java view that?

Answer 33

+ It views it as the whole block of all of them

Question 34

Catch Block

Answer 34

**declares a type and an exception parameter** The catch block can handle exceptions of the specified type Inside the catch block, you can use theparameters identifier to interact wtih a caught exception object **try {** ``` } **catch (FileNotFoundException e)** { System.err.println("FileNotFoundException: " + e.getMessage()); throw new SampleException(e); ``` } **catch (IOException e) { System.err.println("Caught IOException: " + e.getMessage());** }

Question 35

\* Mathematical Formula with a **Try Catch Block**

Answer 35

+ looking for a divide by zero

Question 36

\* Value of a **Null Value**

Answer 36

+ means NO VALUE

Question 37

\* overloading and overwriting

Answer 37

**_ Overloading_** in Java can occur when two or more methods in the same class **share the same name or even if a child class shares a method with the same name as one of it’s parent classes.** When you use the identifier form, there must be exactly one function with the specified name in scope at the pragma location. Attempting to use the identifier form of #pragma weak with an overloaded function is an error. For example: ``` int bar(int); float bar(float); #pragma weak bar // error, ambiguous function name ``` **Overriding** methods is completely different from overloading methods. If a derived class **requires a different definition for an inherited method**, then that method can be redefined in the derived class.

Question 38

How do we name classes?

Answer 38

``` **class _MyClass_** { // field, constructor, and // method declarations } ``` Modifiers such as public, private, and a number of others that you will encounter later. The class name, with the **initial letter capitalized by** convention. The class body, surrounded by braces, {}.

Question 39

Static Methods

Answer 39

Frequently used tasks Prevents you from reinventing the wheel Called by using its class name followed by a dot (.) and method name **Static methods**, which have the static modifier in their declarations, should be invoked with the class name, without the need for creating an instance of the class, as in **ClassName.methodName(args)**

Question 40

Arrays

Answer 40

Make it conenient to process related groups of values. Remain the same in length once they are created although an array variable may be reassigned such that it refers to a new array of a different length uses keyword new use [] n array is a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created. After creation, its length is fixed. ``` **public static void main(String[] args)** { // declares an array of integers int[] anArray; ``` ``` // allocates memory for 10 integers **anArray = new int[10];** ``` ``` // initialize first element anArray[0] = 100; // initialize second element anArray[1] = 200; // etc. anArray[2] = 300; anArray[3] = 400; anArray[4] = 500; anArray[5] = 600; anArray[6] = 700; anArray[7] = 800; anArray[8] = 900; anArray[9] = 1000; ```

Question 41

\*Diff btw subroutine and function

Answer 41

- function will ALWAYS return a value - looks the same though

Question 42

When you open a Java file it would be nice to have a print heading to tell you what the program is along with the creator's name...and the method name

Answer 42

\*Look for any declarations that are global (available for all the methods) \*Imports \*Then look for where the program will start executing \*Main module should be a series of calls to different methods (named so well that you can just read the name and tell what it is doing ex: print document ID numbers) \*Any declarations done as a constant should be done at the top of the program

Question 43

Constructors

Answer 43

constructor is **used in the creation of an object that is an instance of a class**. Typically it performs operations required to initialize the class **before methods are invoked or fields are accessed**. Constructors are never inherited. ## Footnote To create a new Bicycle object called myBike, a **constructor is called by the new operator:** **Bicycle myBike = new Bicycle(30, 0, 8);** new Bicycle(30, 0, 8) creates space in memory for the object and initializes its fields.

Question 44

Floating Point Data

Answer 44

hold real numbers 8.8888 Char holds character data

Question 45

**Each class declaration that begins with keyword \_\_\_\_\_** **must be stored in a file that has exactly the same name as the class and ends with the *.java* file name extension.**

Answer 45

***public***

Question 46

**Keyword _____ in a class declaration is followed immediately by the class's name.**

Answer 46

***class*** ***Ex: pulbic class Welcome1***

Question 47

**Keyword ____ requests memory from teh system to store an object, then calls the corresponding class's constructor to initialize the object**

Answer 47

***new***

Question 48

**BY DEFAULT, CLASSES THAT ARE COMPILED IN THE SAME DIRECTORY ARE CONSIDERED TO BE IN THE SAME PACKAGE, KNOWN AS THE \_\_\_\_\_**

Answer 48

***DEFAULT PACKAGE***

Question 49

**WHEN EACH OBJECT OF A CLASS MAINTAINS ITS OWN COPY OF AN ATTRIBUTE, THE FIELD THAT REPRESENTS THE ATTRIBUTE IS ALSO KNOWN AS A \_\_\_\_\_\_\_\_\_\_\_**

Answer 49

***INSTANCE VARIABLE***

Question 50

**KEYWORD *_PUBLIC_* IS AN ACCESS \_\_\_\_\_\_.**

Answer 50

***MODIFIER***

Question 51

**RETURN TYPE _____ INDICATES THAT A METHOD WILL NOT RETURN A VALUE**

Answer 51

***VOID***

Question 52

**SCANNER METHOD \_\_\_\_\_\_\_** **READS CHARACTERS UNTIL IT ENCOUNTERS A NEWLINE CHARACTER, THEN RETURNS THOSE CHARACTERS AS A *STRING***

Answer 52

***nextLine***

Question 53

**VARIABLE of type float represent _____ floating point numbers**

Answer 53

***SINGLE PRECISION***

Question 54

**The format specifier _____ is used to output values of type float or double**

Answer 54

***%f***

Question 55

**Every method's body is delimited by left and right braces ( *{ }* )**

Answer 55

***_TRUE_***

Question 56

Floating-point values that appear in source code are known as floating-point literals and type float by default

Answer 56

***FALSE*** Such literals are of type ***double*** by default

Question 57

Method Overloading

Answer 57

Methods of the same name can be declared in the same class, as long as they have different sets of parameters.

Question 58

A method is invoked with a \_\_\_\_\_\_

Answer 58

Method call