Basic Java Programming

Teguh Sutanto, M.Kom.

Tujuan

• Mahasiswa dapat menyebutkan berbagai tipe data dan operato

Materi

• Struktur dasar program Java• Variable• Constanta• Tipe Data• Operator

Buku Referensi

•A computer program or application is a set of instructions,

written in a programminglanguage that enables a computer

to perform some specifi ed task

Mengapa Java?

• Java is small and beautiful• Java is object oriented• Java supports the Internet• Java is general purpose• Java is platform independent• Java has libraries

Struktur Program Java

Nama Class (Nama Program)

Isi program “{ }”Method main(String []argz)

Local variable

Penamaan Program/Class

• Kata Benda• Diawali dengan HurufBesar• Nama File = NamaProgram• Contoh: public class ProgramPertamax disimpan dengan nama

ProgramPertamax.java

• Tidak boleh ada spasi• Contoh: Program Pertamax

• Tidak boleh diawali dengan angka• Contoh: 1Program

Method public static void main(String []param)

public static void main(String []param){//code program//alur program}

Parameter Program

Every Java application contains a class with a main method. When the application starts, the instructions in the main method are executed.

Setiap program yang akan dijalankan oleh JVM harus ada method launcher yang dengan nama main(String[] a)

1

2

3

SimpanCompile

Jalankan

dengan nama PrgPertamax.java

>javac PrgPertamax.java

>java PrgPertamax

A keyword is a dictionary word — a word that’s built right into a language

Keywoards

abstract continue for newswitch assert default gotopackage do synchronized booleanif private this breakdouble implements protected throwbyte else import publicthrows case enum instanceofreturn transient catch extendsint short try charfinal interface static voidclass finally long strictfpvolatile const float nativesuper while s e

Alur Program

1. sequences2. repetitions3. selections4. methods5. ready-made objects6. objects you write yourself

Case Sensitive

• The java proGRAMMing lanGUage is case-sensitive. ThIS MEans that if you change a lowerCASE LETTer in a wORD TO AN UPPercase letter, you chANge the wORD’S MEaning. ChangiNG CASE CAN MakE the enTIRE WORD GO FROM BeiNG MEANINGFul to bEING MEaningless.

public static void main(String args[]) { System.out.println(“Chocolate, royalties, sleep”);}

• main: The main starting point for execution in every Java program.• String: A bunch of text; a row of characters, one after another.• System: A canned program in the Java API. (This program accesses

some features of your computer that are outside the direct control of the Java virtual machine (JVM).)• out: The place where a text-based program displays its text. (For a

program running in Eclipse, the word out represents the Console view. • println: Display text on your computer screen

Variable: The Holders of Information

• Sebuah tempat untuk menyimpan data, contoh:• Angka 365 merepresentasikan jumlah hari dalam satu

tahun• Angka 37 derajat celcius menunjukkan suhu normal

tubuh manusia• Nama seorang aktor favorit, Jet Lee

Variable di mata seorang programer

JumlahHari

suhuTubuh

aktorFavoritProgrammer

365

37“Jet Lee”

Variables in algebra are letters of the alphabet, like x and y, but in computer languages, they can also be any descriptive names like sum, answer, or first_value.

Note:

A variable is a named memory location capable of storing data of a specified type

So…what is the var?

• Computer programs manipulate (or process) data. A variable is used to store a piece of data for processing. It is called variable because you can change the value stored.•More precisely, a variable is a named storage location, that

stores a value of a particular data type. In other words, a variable has a name, a type and stores a value.• A variable has a name (or identifier),

e.g., radius, area, age, height. The name is needed to uniquely identify each variable, so as to assign a value to the variable (e.g., radius=1.2), and retrieve the value stored (e.g., radius*radius*3.1416).

Variable…(cont)

• A variable has a type. Examples of type are:• int: for integers (whole numbers) such as 123 and -456;• double: for floating-point or real numbers, such

as 3.1416, -55.66, having an optional decimal point and fractional part;• String: for texts such as "Hello", "Good Morning!". Text

strings are enclosed within a pair of double quotes.

Tipe Data Primitip• byte• short• int• long

Integers• float• double.Floating-point• This group includes char, which represents symbols in a

character set, like letters and numbers.Characters• This group includes boolean, which is a special type for

representing true/false values.Boolean

Deklarasi Variable• A variable must be declared before it can be used.• A variable declaration specifi es• the type of data that the variable can hold, for example int

or double , and• the name of the variable.

varType varName; // Declare a variable of a type varType varName1, varName2,...; // Declare multiple variables of the same type varType varName = initialValue; // Declare a variable of a type, and assign an initial value varType varName1 = initialValue1, varName2 = initialValue2,... ; // Declare variables with initial values

• A variable can store a value of that particular type. It is important to take note that a variable in most programming languages is associated with a type, and can only store value of the particular type. For example, a int variable can store an integer value such as 123, but NOT real number such as 12.34, nor texts such as "Hello". The concept of type was introduced into the early programming languages to simplify intrepretation of data made up of 0s and 1s.

Contoh Variable

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