Pemrograman Dasar Basic Elements Of Java Compiling and

Pemrograman Dasar Basic Elements Of Java

Compiling and Running a Java Application 2

Portable Java App 3

Java Platform: hardware or software environment in which a program runs. Two components: § The Java Virtual Machine § The Java Application Programming Interface (API) 4

Java Platform 5

Typical Java Development Environment

Basic Lexical Elements Character set – 16 -bit Unicode – Legal characters Keywords – Reserved words, special meaning, illegal for identifiers Identifiers – Names of declared entities, e. g. variables, constants Variables – A variable is a storage location, something that can hold a value to which a value can be assigned Literals – Constants or values, e. g. 12, 17. 9, “Hello” 7

Basic Lexical Elements Other notations – Operators, e. g. +, -, *, /, etc. – Block symbols, e. g. pair of {} Comments – Help developers, ignored by compiler – e. g. /* Program 1 */ // Function to count Circle area 8

Character Set Java programs are written using Unicode character set (16 bit), which include: Capital letters: A. . Z Small letters: a. . z Numbers: 0. . 9 Punctuation marks, e. g. ‘!’ , ‘, ’, ’? ’, etc. Other characters or symbols, e. g. – Arithmetic symbols, e. g. ‘+’, ‘-’, ‘/’, etc. – from many natural languages Pengantar Bahasa C - TIF UB 2010 9

Keywords cannot be used as identifiers (reserved) because they have special meaning within the language. Pengantar Bahasa C - TIF UB 2010 10

Identifiers Used for names of declared entities such as variables, constants, and labels Must start with a letter, followed by letters, digits, or both. Identifiers are case-sensitive The terms letter and digit are broad in Unicode: if something is considered a letter or digit in a human language, you can probably use it in identifiers. "Letters" can come from Chinese, Korean, Gurmukhi, Georgian, Devanagari, and almost any other script written in the world today. Pengantar Bahasa C - TIF UB 2010 11

Identifiers Letters also include any currency symbol (such as $, ¥, and £) and connecting punctuation (such as _). Identifiers can be as long as you like, but use some taste. Identifiers that are too long are hard to use correctly and actually obscure your code. Cannot use keywords (e. g. for, if, while, etc) Valid identifiers, e. g. : – name, x 1, _total, cubic Invalid identifiers, e. g. : – 1 kali, int Pengantar Bahasa C - TIF UB 2010 12

(Data) Types Every expression has a type that determines what values the expression can produce. The type of an expression is determined by the types of values and variables used within that expression. Types are divided into the primitive types and the reference types. 13

Primitive Data Types 14

Data Types & Default Values 15

Literals Also known as “values” or “constants” Each (data) type has literals, which are the way that constant values of that type are written. – – – – Boolean literals Character literals Integer literals Floating-point literals String literals Reference literals Class literals 16

Literals Boolean literals – Only true and false Character literals – Appear with single quotes, e. g. ‘Z’, ‘a’, ‘ 2’, ‘u 004 e’ – Certain special characters can be represented by an escape sequence, e. g. : 17

Literals Integer literals – Integer constants are a sequence of octal, decimal, or hexadecimal digits. – The start of a constant declares the number's base: A 0 (zero) starts an octal number (base 8); a 0 x or 0 X starts a hexadecimal number (base 16); and any other digit starts a decimal number (base 10). – E. g. all the following numbers have the same value 29 035 0 x 1 D 0 X 1 d 18

Literals Floating-point literals – Expressed in either decimal or hexadecimal – The decimal form consists of a string of decimal digits with an optional decimal point, optionally followed by an exponent the letter e or E, followed by an optionally signed integer. – e. g. all these literals denote the same floating-point number: 18. 1. 8 e 1. 18 E+2 180. 0 e-1 19

Literals Floating-point literals (continued) – The hexadecimal form consists of 0 x (or 0 X), a string of hexadecimal digits with an optional hexadecimal point, followed by a mandatory binary exponent the letter p or P, followed by an optionally signed integer. – The binary exponent represents scaling by two raised to a power. – e. g. all these literals denote the same floating-point number (decimal 18. 0): 0 x 12 p 0 0 x 1. 2 p 4 0 x. 12 P+8 0 x 120 p-4 20

Literals Floating-point literals (continued) – Floating-point constants are of type double unless they are specified with a trailing f or F, which makes them float constants, such as 18. 0 f. – A trailing d or D specifies a double constant. – There are two zeros: positive (0. 0) and negative (-0. 0). – Positive and negative zero are considered equal when you use == but produce different results when used in some calculations. 21

Literals String literals (continued) – String literals appear with double quotes, e. g. “Welcome”, “salam”, "u 0633u 0644u 0672u 0645". – Any character can be included in string literals, with the exception of newline and " (double quote). – Newlines are not allowed in the middle of strings. – If you want to embed a newline character in the string, use the escape sequence n. – To embed a double quote use the escape sequence ". – A string literal references an object of type String. 22

Variables A variable is a storage location, something that can hold a value to which a value can be assigned. A variable declaration states the identifier (name), type, and other attributes of a variable. e. g. float x, y; // is the same as float x; float y; float x = 3. 14 f, y = 2. 81 f; // is the same as float x = 3. 14 f; float y = 2. 81 f; 23

Variables Instance variables (non-static fields) Class variables (static fields) Local variables Parameters 24

Variables public class Bicycle { int cadence = 0; // instance variable static int wheels = 2; // static variable … // formal parameter: decrement void apply. Brakes(int decrement) { speed = speed - decrement; } // local variable: states void print. States() { String states = "cadence: "+cadence+ ", speed: "+speed+", gear: "+gear; System. out. println(states); } } 25