Programming Fundamentals 1

8/9/2019 Programming Fundamentals 1

1/45

8/21/20108/21/2010 Prepared by Dale D. Miguel SLU CICSPrepared by Dale D. Miguel SLU CICS 11

Programming FundamentalsProgramming Fundamentals

ICS 112 / IT 112ICS 112 / IT 112

This presentation follows the introductoryThis presentation follows the introductorylessonlesson

The introductory lesson covered generalThe introductory lesson covered general

concepts about programming (See Courseconcepts about programming (See CourseNotes 1, 2 and 3)Notes 1, 2 and 3)


2/45


In Java, a program is a classIn Java, a program is a class

/**/**

* Sample java program* Sample java program

*/*/

public class Hellopublic class Hello{{

public static void main(String[] args)public static void main(String[] args) {{

//prints the string "Hello world" on screen//prints the string "Hello world" on screenSystem.out.println("Hello world!");System.out.println("Hello world!");

}}

}}


3/45


A class must have the main method for it toA class must have the main method for it to

be an executable programbe an executable program

/**/**

* Sample java program* Sample java program

*/*/

public class Hellopublic class Hello{{

public static void main(String[] args)public static void main(String[] args) {{

//prints the string "Hello world" on screen//prints the string "Hello world" on screenSystem.out.println("Hello world!");System.out.println("Hello world!");

}}

}}


4/45


Coding Guidelines in JavaCoding Guidelines in Java

Your Java programs should always end with theYour Java programs should always end with the

.java.java extension.extension.

Filenames shouldFilenames shouldmatchmatch the name of yourthe name of your

public class.public class.

For example, if the name of your public class isFor example, if the name of your public class is Hello,Hello,

you should save it in a file calledyou should save it in a file calledHello.javaHello.java..

You should write comments in your codeYou should write comments in your code

explaining what a certain class does, or what aexplaining what a certain class does, or what a

certain method do.certain method do.


5/45


Java CommentsJava Comments

Comments are notes included in a codeComments are notes included in a code

for documentation purposes.for documentation purposes. The comments are not part of the programThe comments are not part of the program

and they do not affect the flow of theand they do not affect the flow of theprogram.program.


6/45


Single Line CommentsSingle Line Comments

Single line comments starts with //.Single line comments starts with //.

All the text after // are treated asAll the text after // are treated ascomments.comments.

For example,For example,

// This is a single line comment// This is a single line comment


7/45


Multiline CommentsMultiline Comments

Multiline comments starts with aMultiline comments starts with a /*/* and ends withand ends withaa */*/..

All text in between the two delimeters (All text in between the two delimeters (/*/* andand */*/ ))are treated as comments.are treated as comments.

Unlike single line comments, the multilineUnlike single line comments, the multilinecomment can span multiple lines.comment can span multiple lines.

For example,For example,/* this is an example of/* this is an example of

multiline comments */multiline comments */


8/45


Special Javadoc CommentsSpecial Javadoc Comments

Special Javadoc comments are used for generating an HTMLSpecial Javadoc comments are used for generating an HTMLdocumentation for your Java programs.documentation for your Java programs.

You can create javadoc comments by starting the line withYou can create javadoc comments by starting the line with /**/** andandending it withending it with */*/..

Like multiline comment, the special javadoc comment can spanLike multiline comment, the special javadoc comment can spanlines. It can also contain certain tags to add more information to yourlines. It can also contain certain tags to add more information to yourcomments. For example,comments. For example,/**/**This is an example of special java doc comments used forThis is an example of special java doc comments used for \\nngenerating an html documentation. It uses tags like:generating an html documentation. It uses tags like:

@author Francisco Balagtas@author Francisco Balagtas@version 1.2@version 1.2*/*/


9/45


Java Statement and BlockJava Statement and Block

AA statementstatement is one or more lines of codeis one or more lines of codeterminated by a semicolon.terminated by a semicolon.

Example of a single statementExample of a single statement

System.out.println(Hello world);System.out.println(Hello world);


10/45


AA blockblock is one or more statements bounded byis one or more statements bounded bya pair of an opening curly brace and closinga pair of an opening curly brace and closingcurly brace that groups the statements as onecurly brace that groups the statements as oneunit.unit.

Block statements can be nested indefinitely.Block statements can be nested indefinitely. Any amount of white space is allowed.Any amount of white space is allowed. Example of a blockExample of a block

public static void main( String[] args )public static void main( String[] args ) {{System.out.println("Hello");System.out.println("Hello");System.out.println("world");System.out.println("world");

} // end of main} // end of main


11/45


Coding GuidelineCoding Guideline

In creating blocks, you can place the opening curlyIn creating blocks, you can place the opening curly

brace in line with the statement, for example,brace in line with the statement, for example,public static void main( String[] args )public static void main( String[] args ){{


or you can place the curly brace on the next line,or you can place the curly brace on the next line,

for examplefor example

public static void main( String[] args )public static void main( String[] args ){{



12/45



You should indent the next statements afterYou should indent the next statements afterthe start of a block, for example,the start of a block, for example,

public static void main( String[] args ){public static void main( String[] args ){

System.out.println("Hello");System.out.println("Hello");

System.out.println("world");System.out.println("world");



13/45


Java IdentifiersJava Identifiers

Identifiers are tokens that representIdentifiers are tokens that representnames of variables, methods, classes, etc.names of variables, methods, classes, etc.

Examples of identifiers :Examples of identifiers :

Hello,Hello,

main,main,

System,System,

outout


14/45



Java identifiers areJava identifiers are casecase--sensitivesensitive. This. Thismeans that the identifier:means that the identifier: HelloHello is not theis not thesame assame as hellohello..

Identifiers must begin with either a letter,Identifiers must begin with either a letter,an underscore _, or a dollar sign $.an underscore _, or a dollar sign $.

Letters may be lower or upper case.Letters may be lower or upper case.

Subsequent characters may use numbersSubsequent characters may use numbers0 to 9.0 to 9.

Note: No space character in the identifier!Note: No space character in the identifier!


15/45



Java keywords, like class, public, void, etc.Java keywords, like class, public, void, etc.

cannot be identifierscannot be identifiers

Keywords are predefined identifiersKeywords are predefined identifiersreserved by Java for a specific purpose.reserved by Java for a specific purpose.


16/45


17/45


Coding GuidelinesCoding Guidelines

For names of classes, capitalize the first letterFor names of classes, capitalize the first letterof the class name.of the class name.

ExampleExample

TThishisIIssAAnnEExamplexampleOOffCClasslassNNameame

For names of methods and variables, the firstFor names of methods and variables, the firstletter of the word should start with a smallletter of the word should start with a smallletter.letter.

ExampleExample tthishisIIssAAnnEExamplexampleOOffMMethodethodNNameame


18/45



In case of multiIn case of multi--word identifiers that areword identifiers that arenot intended as names of classes, usenot intended as names of classes, usecapital letters to indicate the start of thecapital letters to indicate the start of the

word except the first word.word except the first word.

Example:Example:

charArray,charArray,fileNumber,fileNumber,

firstName.firstName.


19/45



Avoid using underscores at the start ofAvoid using underscores at the start of

the identifier such as _read or _write.the identifier such as _read or _write.


20/45


Java LiteralsJava Literals

Literals are tokens that have values thatLiterals are tokens that have values that

do not change or are constant.do not change or are constant. The different types of literals in Java are:The different types of literals in Java are:

Integer Literals, FloatingInteger Literals, Floating--Point Literals,Point Literals,Boolean Literals, Character Literals andBoolean Literals, Character Literals andString Literals.String Literals.


21/45


22/45


FloatingFloating--Point LiteralsPoint Literals

Floating point literals represent decimals withFloating point literals represent decimals withfractional parts. An example is 3.1415. Floatingfractional parts. An example is 3.1415. Floatingpoint literals can be expressed in standard orpoint literals can be expressed in standard orscientific notations. For example, 583.45 is inscientific notations. For example, 583.45 is instandard notation, while 5.8345e2 is in scientificstandard notation, while 5.8345e2 is in scientificnotation.notation.

Floating point literals default to the data typeFloating point literals default to the data typedoubledouble which is a 64which is a 64--bit value. To use a smallerbit value. To use a smallerprecision (32precision (32--bit)bit) floatfloat, just append the f or F, just append the f or Fcharacter.character.


23/45


Boolean LiteralsBoolean Literals

Boolean literals have only two values,Boolean literals have only two values,

truetrue ororfalsefalse..


24/45


Character LiteralsCharacter Literals

Character Literals represent single Unicode characters.Character Literals represent single Unicode characters.A Unicode character is a 16A Unicode character is a 16--bit character set thatbit character set thatreplaces the 8replaces the 8--bit ASCII character set. Unicode allowsbit ASCII character set. Unicode allows

the inclusion of symbols and special characters fromthe inclusion of symbols and special characters fromother languages.other languages. To use a character literal, enclose the character in singleTo use a character literal, enclose the character in single

quote delimiters. For example, the letterquote delimiters. For example, the letteraa, is, isrepresented asrepresented as aa..

To use special characters such as a newline character, aTo use special characters such as a newline character, abackslash is used followed by the character code. Forbackslash is used followed by the character code. Forexample, example, \\n for the newline character, n for the newline character, \\r for ther for thecarriage return, carriage return, \\b for backspace.b for backspace.


25/45


String LiteralsString Literals

String literals represent multiple charactersString literals represent multiple characters

and are enclosed by double quotes.and are enclosed by double quotes.An example of a string literal is,An example of a string literal is, HelloHello

World.World.


26/45


27/45


LogicalLogical -- booleanboolean

A boolean data type represents two states:A boolean data type represents two states:

truetrue andand falsefalse.. Example is,Example is,

boolean result = true;boolean result = true;

The example declares a variable namedThe example declares a variable namedresultresult asas booleanboolean type and assigns it atype and assigns it avalue ofvalue oftruetrue..


28/45


TextualTextual charchar

A character data type (char), represents a singleA character data type (char), represents a singleUnicode character. It must have its literalUnicode character. It must have its literalenclosed in single quotes( ). For example,enclosed in single quotes( ). For example, aa //The letter a//The letter a \\tt //A tab//A tab

To represent special characters like ' (singleTo represent special characters like ' (singlequotes) or " (double quotes), use the escapequotes) or " (double quotes), use the escape

charactercharacter \\. For example,. For example, \\'''' //for single quotes//for single quotes ''\\""'' //for double quotes//for double quotes


29/45


The StringThe String

A String represents a data type thatA String represents a data type thatcontains multiple characters.contains multiple characters.

It isIt is nota primitived

atatype, it isanota primitived

atatype, it isaclass.class.It has its literal enclosed in doubleIt has its literal enclosed in doublequotes().quotes().

Example,Example,

String message=Hello world!String message=Hello world!


30/45


IntegralIntegral byte, short, int & longbyte, short, int & long

Integral data types in Java uses three formsIntegral data types in Java uses three forms decimal, octal or hexadecimal. Examples are,decimal, octal or hexadecimal. Examples are,

22 //The decimal value 2//The decimal value 2

077077 //The leading 0 indicates an octal value//The leading 0 indicates an octal value

0xBACC0xBACC //The leading 0x indicates a hexadecimal value//The leading 0x indicates a hexadecimal value

Integral types hasIntegral types has intint as default data type.as default data type. You can define itsYou can define its longlong value by appending thevalue by appending the

letter l or L.letter l or L.


31/45


Integral types and their rangesIntegral types and their ranges

Integer lengthInteger length Name ofName oftypetype

RangeRange

8 bits8 bits bytebyte ((--2277) to (2) to (277-- 1)1)

16 bits16 bits shortshort ((--221515) to (2) to (21515--1)1)

32 bits32 bits intint ((--223131) to (2) to (23131-- 1)1)

64 bits64 bits longlong ((--226363) to (2) to (26363--1)1)


32/45


Coding GuidelinesCoding Guidelines

In defining a long value, a lowercase L isIn defining a long value, a lowercase L is

not recommended because it is hard tonot recommended because it is hard todistinguish it from the digit 1.distinguish it from the digit 1.


33/45


Floating PointFloating Point float and doublefloat and double

Floating point types hasFloating point types has doubledouble as default data type.as default data type. FloatingFloating--point literal includes either a decimal point or one of thepoint literal includes either a decimal point or one of the

following,following, E or e //(add exponential value)E or e //(add exponential value)

F or f //(float)F or f //(float) D or d //(double)D or d //(double)

ExamplesExamples 3.143.14 //A simple floating//A simple floating--point value (a double)point value (a double) 6.02E236.02E23 //A large floating//A large floating--point valuepoint value 2.718F2.718F //A simple float size value//A simple float size value

123.4E+306D123.4E+306D //A large double value with redundant D//A large double value with redundant D In the example shown above, the 23 after the E in the secondIn the example shown above, the 23 after the E in the second

example is implicitly positive. That example is equivalent toexample is implicitly positive. That example is equivalent to6.02E+23.6.02E+23.


34/45


Floating point types and theirFloating point types and their

rangesranges

Float lengthFloat length Name/TypeName/Type RangeRange

32 bits32 bits floatfloat ApproximatelyApproximately3.4e+38 with 73.4e+38 with 7significant digitssignificant digits

64 bits64 bits doubledouble ApproximatelyApproximately1.7e+308 with 151.7e+308 with 15significant digitssignificant digits


35/45


VariablesVariables

AA variablevariable is an item of data used to storeis an item of data used to storestate of objects.state of objects.

A variable has aA variable has a datatypedatatype andand anameaname..

TheThe datatypedatatypeindicates the type of valueindicates the type of valuethat the variable can hold. Hence, thethat the variable can hold. Hence, thedata type defines the possible values fordata type defines the possible values for

the variable.the variable. TheThe variablenamevariablename must follow rules formust follow rules for

identifiers.identifiers.


36/45


Declaring and InitializingDeclaring and Initializing

VariablesVariables

Syntax for declaring a variableSyntax for declaring a variable

[=initial value]; [=initial value];

Values enclosed in are required values,Values enclosed in are required values,while those values enclosed in [] arewhile those values enclosed in [] areoptional.optional.


37/45


Examples ofVariable DeclarationExamples ofVariable Declaration

/*declareadatatype with variablename/*declareadatatype with variablename

resultand booleandatatype*/resultand booleandatatype*/

booleanresult;booleanresult;

/*declareadatatype with variablename/*declareadatatype with variablenameoptionand chardatatype*/optionand chardatatype*/

charoption;charoption;

option = 'C';option = 'C'; //assign'C'to option//assign'C'to option

/*declareadatatype with variablename/*declareadatatype with variablename

grade,doubledatatypeand initializedto 0.0*/grade,doubledatatypeand initializedto 0.0*/

doubledouble grade = 0.0;grade = 0.0;


38/45


Coding Guidelines:Coding Guidelines:

It always good toIt always good to initializeinitialize your variables as you declare them.your variables as you declare them.

UseUse descriptivedescriptive names for your variables. Like for example, ifnames for your variables. Like for example, ifyou want to have a variable that contains a grade for a student,you want to have a variable that contains a grade for a student,name it as,name it as, gradegrade and not just some random letters you choose.and not just some random letters you choose.

Declare one variable per line of code.Declare one variable per line of code. For example, the variable declarations,For example, the variable declarations,

double exam=0;double exam=0;

double quiz=10;double quiz=10;

double grade = 0;double grade = 0;

is preferred over the declaration,is preferred over the declaration, double exam=0, quiz=10, grade=0;double exam=0, quiz=10, grade=0;


39/45


Reading values from theReading values from the

keyboardkeyboard

For some applications, values to be assigned toFor some applications, values to be assigned tovariables are entered through the keyboard duringvariables are entered through the keyboard duringprogram execution. Java provides a mechanism forprogram execution. Java provides a mechanism for

connecting the keyboard to the program. Theconnecting the keyboard to the program. Themechanism involves the so called Stream classes( to bemechanism involves the so called Stream classes( to bestudied later.).studied later.).

In the mean time, the Keyboard class may be used.In the mean time, the Keyboard class may be used.

By using the class Keyboard, values may be assigned toBy using the class Keyboard, values may be assigned toa variable.a variable.

NoteNote:: Copy and save the Keyboard.java program in theCopy and save the Keyboard.java program in thedirectory where you are saving your programsdirectory where you are saving your programs..


40/45


Using the KeyboardReader classUsing the KeyboardReader class

Suppose age is assigned an integer value:Suppose age is assigned an integer value:age = Keyboard.readInt();age = Keyboard.readInt();

Suppose rate is assigned a floating point value( i.e.Suppose rate is assigned a floating point value( i.e.number with decimal digits):number with decimal digits):

rate = Keyboard.readFloat();rate = Keyboard.readFloat();ororrate = Keyboard.readDouble();rate = Keyboard.readDouble();

Suppose choice is assigned a character value:Suppose choice is assigned a character value:choice = Keyboard.readChar();choice = Keyboard.readChar();

Suppose name is a string value(i.e. sequence ofSuppose name is a string value(i.e. sequence ofcharacters):characters):

name = Keyboard.readString();name = Keyboard.readString();


41/45


OutputtingVariable DataOutputtingVariable Data

int value = 10;int value = 10;

char x;char x;

x = A;x = A;System.out.println( value );System.out.println( value );

System.out.println( The value of x= + x );System.out.println( The value of x= + x );


42/45


Formatting a Number OutputFormatting a Number Output

long n = 461012;long n = 461012;System.out.printf("%d%n", n);System.out.printf("%d%n", n);System.out.printf("%08d%n", n);System.out.printf("%08d%n", n);System.out.printf("%+8d%n", n);System.out.printf("%+8d%n", n);System.out.printf("%,8d%n", n);System.out.printf("%,8d%n", n);System.out.printf("%+,8d%n%n", n);System.out.printf("%+,8d%n%n", n);double pi = Math.PI;double pi = Math.PI;System.out.printf("%f%n", pi);System.out.printf("%f%n", pi);

System.out.printf("%.3f%n", pi);System.out.printf("%.3f%n", pi);System.out.printf("%10.3f%n", pi);System.out.printf("%10.3f%n", pi);System.out.printf("%System.out.printf("%--10.3f%n", pi);10.3f%n", pi);


43/45



long n = 461012;long n = 461012;System.out.format("%d%n", n);System.out.format("%d%n", n);System.out.format("%08d%n", n);System.out.format("%08d%n", n);System.out.format("%+8d%n", n);System.out.format("%+8d%n", n);System.out.format("%,8d%n", n);System.out.format("%,8d%n", n);System.out.format("%+,8d%n%n", n);System.out.format("%+,8d%n%n", n);double pi = Math.PI;double pi = Math.PI;System.out.format("%f%n", pi);System.out.format("%f%n", pi);

System.out.format("%.3f%n", pi);System.out.format("%.3f%n", pi);System.out.format("%10.3f%n", pi);System.out.format("%10.3f%n", pi);System.out.format("%System.out.format("%--10.3f%n", pi);10.3f%n", pi);


44/45


Formatted OutputFormatted Output

461012461012

0046101200461012

+461012+461012

461,012461,012+461,012+461,012

3.1415933.141593

3.1423.142

3.1423.142

3.1423.142


45/45



long n = 461012;long n = 461012;System.out.format("%d%n", n);System.out.format("%d%n", n); //461012//461012System.out.format("%08d%n", n);System.out.format("%08d%n", n); // 00461012// 00461012

System.out.format("%+8d%n", n);System.out.format("%+8d%n", n); // +461012// +461012

System.out.format("%,8d%n", n);System.out.format("%,8d%n", n); // 461,012// 461,012

System.out.format("%+,8d%n%n", n);System.out.format("%+,8d%n%n", n); // +461,012// +461,012

double pi = Math.PI;double pi = Math.PI;

System.out.format("%f%n", pi);System.out.format("%f%n", pi); //// 3.1415933.141593

System.out.format("%.3f%n", pi);System.out.format("%.3f%n", pi); ////3.1423.142System.out.format("%10.3f%n", pi);System.out.format("%10.3f%n", pi); //// 3.1423.142System.out.format("%System.out.format("%--10.3f%n", pi);10.3f%n", pi); //// 3.1423.142

Documents

Programming Fundamentals 1