COP 2210 Final Review

By Francisco R. Ortega

Disclaimer

• This is not intended to be a full or official review.

• You are responsible to study and know all the materials

• This cannot replace missed lectures or labs

• Study yours notes , labs, homework and online notes provided to you.

• If information here is beyond the scope of class, ignore it.

Working with Classes

• Create an object

– MyClass C = new MyClass(20);

• Call a method

– Int myValue = C.GetValue();

– C.Setvalue(10);

Create a ClassClass MyClass { //beginning of class declaration

private int value=0; // Instance Variable

MyClass(int value) { //constructor

this.value = value;

}

int getValue() { // Accessor/Getter Method

return this.value;

}

void setValue(int value){ // Mutator/Setter Method

this.value = value

}

}//end of class

Math Operators

Operator

Meaning

Precedence

* , / , %

Multiplication, Division,

Integer ModulusHighest

+ , -

Addition, Subtraction,

Unary Positive and NegativeLowest

Overloading Constructors/Methods

public BankAccount (String acctNum, doubleinitialBalance){

accountNumber = acctNum ;

balance = initialBalance ;

}

public BankAccount(String acctNum){

accountNumber = acctNum ;

balance = 0 ;

}

Integer Division / Mod

Integer Division

Examples: 10 / 4 = 2 9 / 5 = 1 99 / 100 = 0

Unknowingly dividing one integer by another and expecting a “real” result is an extremely common source of logic errors!!!

Integer Mod

Examples: 10 % 4 = 2 9 % 5 = 4 99 % 100 = 99

For both integer division and modulus, the right-hand operand must be non-zero. Otherwise, the Arithmetic Exception “/ by zero” will be thrown.

Math Function

NameNumber of

ArgumentsArgument Type Type Returned Returns

sqrt 1 int or double doubleThe nonnegative square root

of the argument

abs 1 int or double same as the argumentThe absolute value (“distance

from zero”) of the argument

min 2 int or double same as the argumentThe lesser of the

two arguments

max 2 int or double same as the argumentThe greater of the

two arguments

pow 2 int or double doubleThe first argument raised to

the power of the second

round 1 double longThe argument rounded to the

nearest integer, as a long

Math Functions

• double v1 = 10.0;

• double v2 = 2.0;

• double v3 = 3.6;

• double v4 = -3.6;

• double s = Math.sqrt(v2);

• double p = Math.pow(v1, v2);

• double a = Math.abs(v2 - v1);

• double r = Math.round(v3);

• double m1 = Math.max(v1, v2);

• double m2 = Math.min(v3, v4);

JOptionPane

String input =

JOptionPane.showInputDialog(null,"What is the

amount due?", “AMOUT DUE

TITLE",JOptionPane.QUESTION_MESSAGE) ;

Double inputValue = Double.parseDouble(input);

JOptionPane.showMessageDialog(null, “The amout

due is” + inputValue);

Decision Making(Selection or Conditional Execution)

Relational Operators

Algebra Java Meaning

< < less than

≤ <= less than or equal to

> > greater than

≥≥≥≥ >= greater than or equal to

= == equals

≠≠≠≠ != does not equal

Relational Operators and Expressions

Example:

Math.pow(b,2) – 4 * a * c < 0

IF STATMENTS

if (a == “10”)

runMyApp1();

else if (a == “20”)

runMyApp2();

else

runMyApp3();

if (a == “10”)

{

runMyApp1();

}

Else

{

runMyApp2();

}

Nested if statements!

if (a == 10 && a == b)

{

c = a +b;

d = 1;

if (c == 30)

d = 0;

}

if (a == 10)

{

//do something

if (a == b)

{

// do something else

}

}

Truth Tables

A B !B A && B A || B

0 0 1 0 0

0 1 0 0 1

1 0 1 0 1

1 1 0 1 1

Operator Presedence

!highest

*, /, %, +, -

>, >=, <, <=, ==, !=

&&

||lowest

• It is not necessary to enclose relational expressions in parentheses when they are joined by && or ||– relationals have higher precedence than these

operators

– a && b && c is the same as a && (b && c)

• Since ! has the highest precedence of all, it isnecessary to use parentheses – !a > b is not the same as !(a > b)

• It is probably a good idea to always use parentheses with boolean expressions

Operators…

IterationRepetitions or Looping

While and Do While

while (boolean expression)

{

statement(s)

}

do

{

statement(s)

}

while (boolean expression) ;

FOR LOOP

for (initialization action ; boolean expression ; update action)

{

statements ;

}

for (int i=0 ; i < 20 ; i++)

{

statements ;

}

for (int i=0,j=0; i < 10;i++,j+=i + 2)

System.out.println("i:" + i + ";j:" + j);

Know your scanner!import java.util.Scanner ;

Scanner scan = new Scanner(new file(“a.txt”) ;

While (scan.hasNext())

{

//say file is Name age .For example(Frank 35)

Scanner scan2 = new Scanner(scan.next());

String n = scan2.next();

int age = scan2.nextInt();

}

Random Numbers

Random r= new Random() ;

double d 1 = r.nextDouble();//assigns some random double value to x such that 0.0 <= x < 1.0

int num = generator.nextInt()

int num = generator.nextInt(50) // 0 to n-1

Random Numbers

• range a..b (inclusive)

– nextInt( b – a + 1 ) + a

• NUMBER between 10 to 99

– Either:

• nextInt( 99 – 10 + 1 ) + 10

• nextInt( 90 ) + 10

Random Numbers Common Errors

for (int i = 1 ; i <= 10 ; i++)

{

Random r = new Random() ;

int randNum = r. nextInt() ;

System.out.println(randNum) ;

}

How do we fix it?

Wrapper Classes

Primitive Type Wrapper Class

double Double

int Integer

boolean Boolean

char Character

ArrayList<Integer> list = new ArrayList<Integer>() ;

ArrayList Operations

• ArrayList<TYPE> myList = new ArrayList<TYPE>();

• TYPE a = list.get(index);

• list.add(a); //add object to list.

• list.set(index,a); //changes object a in pos index.

• list.add(index,a); //add object a at pos index & shift

• list.remove(index); //deletes object @ specific index.

• list.clear(); //removes all

• list.size(); // finds size of list.

• list.isEmpty(); // true or false depending if list empty

Files

• Reading a file into a scanner

– Scanner fileIn = new Scanner( new File ( “Votes.in”) );

• Writing to a file

– Example 1:

• PrintWriter outFile = new PrintWriter("Output.txt") ;

– Example 2:• File outputFile = new File("results.txt")

• PrintWriter out = new PrintWriter(outputFile) ;

• Close a file

– outfile.close() ;

Files: OUTPUT

PrintWritter pw = new PrintWritter(“o.txt”);

pw.println(“First Line”);

pw.print(“second”);

pw.print(“ line”);

pw.println(“third line”);

pw.close();

Designing Classes

• Read UNIT 10 and bring questions for Thursday

and Review this weekend.

• Remember that java passes all parameters by

VALUE (COPY)

– Also remember, that the variable that holds your

objects is just a memory reference.

• Therefore, you can modify the object you pass.

• Ask Frank Hernandez about review this weekend

– His email is fhern006@fiu.edu

Has-A vs is-A

• Has-A / Aggregation / Composition

– Dealer has a Car

– PokerHand has a Card

• Is-a / Inheritance

– A Student is a Person

– A TexasHoldemPoker is a PokerGame

• Helper Classes

– Card.ShowCard() helps Hand.ShowHand()

Static!!!! STATIC !!!

• Static variable: – private static int howMany= 0 ;

• Using the static within the constructor:– public CarDealer(String name)

{//some codehowMany++; }

• Static functions:– public static int getHistoricalCarCountInDealer()

{

return howMany;

}

STRINGS!

• String magic = “Abracadabra!”

• int pos = magic.indexOf("A") ; // pos gets 0

• pos = magic.indexOf("Abra") ; // 0 again

• pos = magic.indexOf("abra") ; // pos gets 7

• pos = magic.indexOf('b') ; // pos gets 1

• pos = magic.indexOf(magic) ;// 0 WHY?

• pos = magic.indexOf(“XYZ”); // -1 WHY?

• pos = magic.indexOf(‘a’,4); //pos gets 5

– (the 5th character),

String

• String magic = "Abracadabra!" ;

• String sub = magic.substring(0,4) ; // sub gets "Abra"

• sub = magic.substring(0,1) ; // "A"

• sub = magic.substring(4,7) ; // "cad"

• sub = magic.substring(0,magic.length()) ;

• String word = "ada" ;

• sub = magic.substring(magic.indexOf(word),11) ;

More about Strings

• StringIndexOutOfBoundsException

• string-object.toUpperCase()

• string-object.toLowerCase()

• string-object.charAt(index)

• STRINGS ARE IMMUTABLE

• If myString.equals(“Francisco”)

– You cannot do ==

• If myString.equalsIgnoreCase(“francisco”)

SOLVE

String s1 = new String("abcdef");

String s2 = new String("123abc");

What are the values of the following expressions?

a. s1.substring(3)

b. s1.substring(1,4)

c. s1.charAt(0) == s2.charAt(3)

d. s1.substring(0,3).equals(s2.substring(4))

String / CompareTo Method

• int a = s1.compareTo(s2)

• a is negative if s1 is less than s2

• a is zero if s1 is equal to s2

• a is positive if s1 is greater than s2

• Strings are compare as they would appear in the dictionary

• If (s1.compareTo(s2) > 0) …

• Also you can use compareToIgnoreCase

String – compareTo… HOW?

Review Questions from Book

• The following questions come from Edition 3.

They may be similar to your current edition

Chapter 5

Chapter 5

Chapter 5

Chapter 5

Chapter 5

Chapter 6

Chapter 6

Chapter 7

Chapter 8

Chapter 8

Questions

• Study hard…. GOOD LUCK!