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CS111: PROGRAMMING

LANGUAGE II

Lecture 1: Introduction Computer Science

Department

1

Lecture Contents

Dr. Amal Khalifa, 2014

Course info

Why programming??

Why Java ??

Write once, run anywhere!!

Java basics

Input/output

Variables

Expressions

Conditions

Loops

Methods

Arrays

2

Course info


Website

http://cs111spr14.wordpress.com/

Book

Course plan

Assessment methods and grading

Labs and practical assignments

The term Project

3







Quiz!!!!

What is a program? (instructions)

What is a programming language? (syntax/rules)

What is a Software Package? (application domain)

4


Why Programming?? 5

Programming Enables you to make a computer do

anything you want.

First challenge. Learn a programming language.

Next question. Which one?


Why Java??

It’s not about the language!

Develop general programming skills applicable to

many languages

Javatar!!

6


Why Java?

Clarity - Keep it Simple

Relatively easy graphics

and GUI programming

Lots of library packages

Full documentation

http://java.sun.com

Colleges are teaching it

Companies are using it

Students want it

Teachers welcome it... ;)

Programmers drink it... :)

Free compiler and IDEs

7


Java == class

Everything must be in a class. There are no

global functions or global data.

What about main??

8


Your first Java program.. 9


The Code life Cycle!!

Edit compile run

10


http://images.google.com.eg/imgres?imgurl=http://intercodes.files.wordpress.com/2007/09/eclipse_logo_30.gif&imgrefurl=http://www.harrynorthover.com/blog/2008/07/08/which-ide/&usg=__lh1ekTeGtq1yytiYHDkUskhOKt8=&h=330&w=500&sz=82&hl=en&start=14&sig2=rQXgXcobsNGerNZtNnFBKg&zoom=1&itbs=1&tbnid=rFfVzEr-s4uB7M:&tbnh=86&tbnw=130&prev=/images?q=java+IDE&hl=en&rlz=1T4ADBS_enEG293EG294&tbs=isch:1&ei=6DSsTPu2Bc-J4Qby4PSwBw

http://images.google.com.eg/imgres?imgurl=http://www.prodeveloper.org/wp-content/uploads/2008/10/netbeans0.png&imgrefurl=http://www.prodeveloper.org/&usg=__5kYv8kBSnsmtuY8_Gijwdb9Eh-U=&h=218&w=243&sz=72&hl=en&start=11&sig2=ZqXAx2qY58gX_pwJRuY1Vw&zoom=1&itbs=1&tbnid=BNytUNr4x3-1CM:&tbnh=99&tbnw=110&prev=/images?q=netbeans+logo&hl=en&rlz=1T4ADBS_enEG293EG294&tbs=isch:1&ei=NTWsTJzXKIKC4QbbkYGsBw

Write once, Compile Anywhere! 11


Your first Java program.. 12

// indicates a

comment.

class keyword

Java is case

sensitive

braces { , }

delimit a

class body

main Method


“Everything must be in a class”

There are no global functions or global data.

Basic language elements 13


Text I/O

Standard output.

Flexible OS abstraction for output.

In Java, applications use the standard output object

(System.out) to display text on terminal.


14

Command line output 15

Multiple line

O/P

Formatting

output

public class TestIO {

public static void main(String[] args)

{

System.out.println(“Welcome to java”);

System.out.println(“Welcome to \n java”);

System.out.print(“Welcome to”);

System.out.println(“java”);

System.out.printf(“%s\n%s\n“, “Welcome

to”,”java”);

}

}

}


Common escape sequences


16

Printf Conversion-Characters


17

Strings & Text

String msg1 = new String( “Hello” );

String msg2 = “Hello” ;

String msg3 = “Year “ + 2005; //valid??

18


Standard Input

input is received from Terminal window.

Input entered while program is executing.


19

Reading values


use : import java.util.Scanner;

Define an object of the Scanner class:

Scanner input = new Scanner(System.in);

input values:

num1 = input.nextInt();

Display after calculation:

System.out.printf(“the square is : %d

\n”, num1*num1);

20

example 21


example


22

variables

Declaration, memory allocation, initialization

int total = 0;

int count, temp, result;

Multiple variables can be created in one declaration

data type variable name


23

Constants


A “constant variable” is an identifier that is similar to a

variable except that it holds one value for its entire existence

Why constants:

give names to otherwise unclear literal values

facilitate changes to the code

prevent inadvertent errors

In Java:

final double PI = 3.14159265;

24

Arithmetic Expressions

An expression is a combination of operators and operands

Arithmetic expressions (we will see logical expressions later)

are essentially special methods applied to numerical data

objects: compute numeric results and make use of the arithmetic

operators:

Addition +

Subtraction -

Multiplication *

Division /

Remainder %


25

Assignment-related Operators

Increment and decrement operators: ++, --

Assignment operators: +=, -=, *=, /=

count = count + 1;

count += 1;

count ++;

count = count - 10;

count -= 10;

these three expressions have the same effect

these two expressions have the same effect


26

Operator Precedence

What is the order of evaluation in the following expressions?

a + b + c + d + e

4 3 2

a + b * c - d / e

3 2 4 1

a / (b + c) - d % e

2 3 4 1

a / (b * (c + (d - e)))

4 1 2 3

1


27

How Do Data Conversions Happen?

Implicitly:

occurs automatically

uses widening conversion,

Examples: 4.0 / 8 (which / is it: double/double, float/float, int/int)

4 / 8.0 (which / is it: double/double, float/float, int/int)

4 + 5 / 9 + 1.0 + 5 / 9 / 10.0 (what is the value?)


28

How Do Data Conversions Happen?


29

Explicitly: Casting

widening / narrowing conversions

Examples: double MyResult;

MyResult = 12.0 / 5.0; //OK

int myInt = (int) MyResult; // truncation

MyResult = (double)myInt/3.0;

Be careful!!

Example: in 1996, Ariane 5 rocket exploded after

takeoff because of bad type conversion.


30

Class Math

All Math class methods are static

Each is called by preceding the name of the method with the class name Math and the dot (.) separator

Method arguments may be constants, variables or expressions


31

Dr. Amal Khalifa, 2014 32

Example

Solve quadratic equation ax2 + bx + c = 0.

public class Quadratic {

public static void main(String[] args) {

double a,b,c,d;

// input coefficient values..

// calculate roots

d = Math.sqrt(b*b - 4.0*a*c);

double root1 = (-b + d) / (2.0*a);

double root2 = (-b - d) / (2.0*a);

// print them out

System.out.println(root1);

System.out.println(root2);

}

}


33

Lecture Contents


Java basics (part II)

34

Conditions & Branching


35

Conditional Statements

A conditional statement lets us choose which

statement will be executed next

Conditional statements give us the power to make

basic decisions

Java's conditional statements:

the if and if-else statements

the conditional operator

the switch statement


36

The if Statement

The if statement has the following syntax:

if is a Java

reserved word

The condition must be a boolean expression.

e.g., a boolean variable, a == b, a <= b.

It must evaluate to either true or false.

If the condition is true,

this statement is executed.

if ( condition )

statement1;

else

statement2;

If the condition is false,

this statement is executed. Dr. Amal Khalifa, 2014

37

•Several statements can be grouped together into a block statement

•A block is delimited by braces ( { … } )

Logic of an if-else statement

true false

condition

evaluated

Statement 1 Statement 2


38

Relational operators


39

Logical Operators


40

Loops & Iterations


41

Loop Statements

while statement

do statement

for statement

while ( condition )

statement;

do

{

statement list;

} while ( condition );

for ( initialization ; condition ; increment )

statement;


42

while ( condition )

statement;

While loops


43

Example

Look at

the code

and

describe

the

output !!

// set initial value of month so that the while condition

// below is false initially

int month = -1;

while (month < 1 || month > 12)

{

System.out.print( “Enter a month (1 to 12): “);

month = scan.nextInt();

}


int month = scan.nextInt();

while (month < 1 || month > 12)

{

System.out.println( month + “ is not a valid month.” );



}


44

do { statement; } while ( condition );

do loops


45

Example

What is

the

difference

here??


int month; // no need to initialize month

do

{

System.out.print( “Enter a month(1 to 12): “);


} while (month < 1 || month > 12);

// beginning of the next statement

46

for ( initialization ; condition ; increment )

statement;

for loops


47

Example

int sum = 0;

for (int counter = 1; counter <= max; counter++)

sum += counter;

// beginning of the next statement

counter++

Establish initial value of control variable.

Determine if final value of control

variable has been

reached.

counter <= max sum+= counter

true

false

int counter = 1

Body of loop (this may be

multiple statements)

Increment the

control variable.


48

Methods

A method:

groups a sequence of statement

takes input, performs actions, and produces output

In Java, each method is defined within specific class


49

Method Declaration: Header

A method declaration begins with a method header

method

name

return

type

parameter list

The parameter list specifies the type and name of each parameter The name of a parameter in the method

declaration is called a formal argument

public class MyClass

{

static int min ( int num1, int num2 ) …

properties Dr. Amal Khalifa, 2014

50

Method Declaration: Body

The header is followed by the method body:

static int min(int num1, int num2)

{

int minValue = num1 < num2 ? num1 : num2;

return minValue;

}

class MyClass

{ …

…

}


51

The return Statement

The return type of a method indicates the type of

value that the method sends back to the calling

location

A method that does not return a value has a void

return type

The return statement specifies the value that will be

returned

Its expression must conform to the return type


52

Calling a Method

Each time a method is called, the values of the actual arguments in the invocation are assigned to the formal arguments

static int min (int num1, int num2)

{

int minValue = (num1 < num2 ? num1 : num2);

return minValue;

}

int num = min(2, 3);


53

Method Call Stack

A method can call another method, who can call

another method, …

min(num1, num2, num3)

println()

…println(…)

min(1, 2, 3);

main


54

What is an array?


Array

data structures

Group of variables (called elements) containing values of the same type.

related data items of the same type.

fixed length once created.

Elements referred to using index or subscript.

In java, Arrays are objects, so they’re considered reference types.

Every array object knows its own length and stores it in a length instance variable.

Elements can be either primitive types or reference types (strings).

55

An index must be a nonnegative integer.

Can use an expression as an index

Every array object knows its own length and stores it in a length instance variable

Array elements


56

7.3 Arrays in Java

declare

create

initialize

int[] a;

int a[];

a = new int[5];

for(int i=0;i<5;i++)

a[i] = i*i;


57

Com

mon

Op

era

tions

Dr. Amal Khalifa, 2014 58

Welcome to the java world!!

That’s all …..


59

CS111: PROGRAMMING LANGUAGE II - WordPress.com · · 2015-08-22Why programming?? ... System.out.printf(“%s\n%s\n“, “Welcome to”,”java”); } ... System.out.print( “Enter

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