Dasar Pemrograman Java

Transkripsi

1 Dasar Pemrograman Java Nurochman

2 Sejarah Java Pada 1991, sekelompok insinyur Sun dipimpin oleh Patrick Naughton dan James Gosling menggarap Proyek Green Tujuan merancang bahasa komputer untuk perangkat konsumer seperti cable TVBox: memori kecil dan prosesor yg macam2 Mulanya bahasa yang diciptakan diberi nama Oak oleh James Gosling Nama JAVA sendiriterinspirasipadasaatmereka pada saat sedang menikmati secangkir kopi di sebuah kedai kopi

3 Karakteristik Sederhana : mirip C++, tanpa pointer, single Inheritance, automatic memory allocation dan memory garbage collection. Berorientasi objek (Object Oriented) Dapat didistribusiib i dengan mudah : libraries i networking yang terintegrasi pada Java. Interpreter t (JVM) > > multi platform ltf Robust : runtime Exception handling Aman: mekanisme keamanan untuk menjaga aplikasi lk tidak digunakan untuk merusak sistem komputer

4 Karakteristik Architecture Neutral: platform independent Portabel: program Java dapat dengan mudah dibawa ke platform yang berbeda beda tanpa harus dikompilasi ulang Performance: Namun performance Java dapat ditingkatkan menggunakan kompilasi Java lain seperti buatan Inprise, Microsoft ataupun Symantec yang menggunakan Just In Time Compilers (JIT). Multithreaded Dinamis : penambahan fitur pd sebuah class tidak mengganggu program yg menggunakan class tsb.

5 Fitur Java Java Virtual Machine (JVM) melakukaninterpretasiterhadap bytecode yg dihasilkan dr proses kompilasi Garbage Collection mencegah memory leaks. Code Security

6 Elemen Bahasa Java Types Literals Variables Operators Control Structures Exceptions Arrays

7 Tipe Data Tipe data primitif Tipe data reference

8 Tipe data primitif char: unicode (2 bytes each!) Integral types byte: 8 bit signed d2' 2's complement tinteger Short:16 bit signed 2's complement integer int: 32 bit signed 2's complement integer long: 64 bit signed 2's complement integer Floating Point float 32 bit IEEE 754 double 64 bit IEEE 754 (double precision) boolean: true or false only not like C/C++: 0 doesn't mean false!

9 Numbers Integers Four integer types byte 8 bits short 16 bits int 32 bits long 64 bits

10 Numbers Floating Points Two types float and double Float Double Size 32 bits 64 bits Largest Value ±3.4E+38 ±1.79E308 Smallest Value ±1.4E 45 ±4.9E 324 Precision 6 7 sig. figs sig. figs.

11 Characters 16 bit Unicode values Equivalent to a short integer value May assign int to char char thechar = 48; May assign char to int int number = 'a';

12 booleans Can be true or false Declared withthekeyword boolean Declared with the keyword boolean boolean flag = true;

13 Tipe Reference Everything that is not a primitive type is a reference type. Three kinds of reference types: Classes Arrays Interfaces

14 Literal Numbers Integer Normally 32 bits ( to ) Can be long integer i.e. 64 bits Can be expressed in hex or octal Floating Point any number with a decimal point can be expressed in exponential form Integers are normally 32 bits long but long integers are 64 bits long. a = 2; Here 2 is a 32 bit integer literal a = 2L; Here 2 is a 64 bit integer literal

15 Literal Hexadecimal values can be used by prefixing a value 0x or 0X (zero x) a = 0xD; The variable a is set to 13 (Hexadecimal D) Octal values are prefixed with an 0 (zero) b = 055; The variable b is set to 45 ((5*8)+5).

16 Exponential Format Floating point values can also be expressed in exponential form Append a trailing e or E and the exponent value. a = 2.0E1; sets a to 2*10 which is equal to 20 a = 20E2;sets 2.0E2; a to 2*100 which is equal to 200

17 Float VS Double Java supports two floating point types float and double Literal numerics with a decimal point are assumed to be double unless an 'f' suffix is used float vatrate = 17.5f

18 Literal Characters 16 bit values in single quotes Unicode values recognised escape sequences Booleans true false

19 Literal Strings zero or more characters in " (double quote marks) a = ""; (empty string) b = "Hello World\n"; c = "The string \"Hello World\"";

20 Idetifiers Names for classes, variables, methods in Java Must begin with an alphabetic character Can contain upper and lower case letters, numbers, _ and $ Some names are reserved

21 Examples face is a valid identifier 1face is invalid, it begins with a number face% is invalid because % is not allowed face3 is valid Face is valid but is not the same as face

22 Naming Convention Variable and method names normally start with a lower case letter Words within the name are capitalised heightofbox Class names begin with a capital letter HelloWorldApplet

23 Declarations byte age, month; short time; int x; long hours; float phase; double distance; char initial, input; boolean flag; int x=1,z=4,t; double phase = 4e3.6; float w=3e7.3f; 3f; char alpha='a'; boolean flag=true,p;

24 Initialising Declarations can appear anywhere in code Variables must be initialised before being used int i; i=i+1; syntax error!

25 Variables Storage location (chunk of memory) and an associated type. type is either a primitive type or a reference type. For primitive i i type variables, ibl a variable ibl holds the actual value (the memory is used to store the value). For reference type variables, a variable holds a reference to an object.

26 Variable Names Variable names are identifiers (so are class names, interface names, method names,...) Identifiers are made of any length sequence of ltt letters, digits it and the underscore character '' '_'. The character '$' is also supported, but is generally only used by code generators, not by humans. The first character of an identifier must not be a The first character of an identifier must not be a digit.

27 Kinds of variables There are lots of kinds of variables, we will bump in to the various kinds as we go... class variables (static) instance variables parameters (method, constructor, exception handler) local lvariables array components

28 Konstanta Kata kunci final class Calendar { } final int monthsinyear = 12; monthsinyear can t be changed

29 Java Comments Block comments /*.. */ Single line comments // This comment terminates at the end of the line Documentation comments /**.. */

30 Casting Allows the type of an expression to be explicitly changed Follows C/C++ syntax: (type) variable name eg e.g. float x = 3.5f; int a = (int) x;

31 Pertanyaan???