Pemrograman Dasar. Basic Elements Of Java

Transcription

1 Pemrograman Dasar Basic Elements Of Java

2 Compiling and Running a Java Application 2

3 Portable Java Application 3

4 Java Platform Platform: hardware or software environment in which a program runs. Oracle has two products that implement Java Platform Standard Edition (Java SE) 7: Java SE Development Kit (JDK) 7 Java SE Runtime Environment (JRE) 7. 4

5 Java Platform SE 7 5

6 Typical Java Development Environment

7 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

8 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

9 Character Set Java programs are written using Unicode character set (16 bit), which include: Capital letters: A.. Z Small letters: a.. z Numbers: 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

10 Keywords Keywords cannot be used as identifiers (reserved) because they have special meaning within the language. abstract continue for new switch assert default goto package synchronized boolean do if private this break double implements protected throw byte else import public throws case enum instanceof return transient catch extends int short try char final interface static void class finally long strictfp volatile const float native super while Pengantar Bahasa C - TIF UB

11 Identifiers (Naming) 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

12 Identifiers (Naming) 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, x1, _total, cubic Invalid identifiers, e.g.: 1kali, int Pengantar Bahasa C - TIF UB

13 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 = 3.14f, y = 2.81f; // is the same as float x = 3.14f, y = 2.81f; // is the same as float x = 3.14f; float y = 2.81f; 13

14 Variables Instance variables (non-static fields) Class variables (static fields) Local variables Parameters 14

15 Variables public class Bicycle { int cadence = 0; // instance variable static int wheels = 2; // static variable // formal parameter: decrement void applybrakes(int decrement) { speed = speed - decrement; } // local variable: states void printstates() { String states = "cadence: "+cadence+ ",speed: "+speed+", gear: "+gear; System.out.println(states); } } 15

16 (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. 16

17 Primitive Data Types Type Contains Default Size Range (for fields) boolean true or false 1 bit NA false char Unicode '\u0000' 16 bits or 0 to or character unsigned 2 bytes '\u0000' (0) to '\uffff' byte short int Signed integer Signed integer Signed integer (65535) 8 bit or -2 7 to or 1 byte -128 to bit or to or 2 bytes to bit or to or 4 bytes to long Signed integer float IEEE 754 floating point 0.0f singleprecision double IEEE floating point doubleprecision 0 64 bit or to or 8 bytes to bit or 1.4E-45 to E+38 4 bytes 64 bit or 439E-324 to 8 bytes E

18 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 18

19 Literals Boolean literals Only true and false Character literals Appear with single quotes, e.g. Z, a, 2, \u004e Certain special characters can be represented by an escape sequence, e.g.: \n newline (\u000a) \t tab (\u0009) \b backspace (\u0008) \r return (\u000d) \f form feed (\u000c) \\ backslash itself (\u005c) \' single quote (\u0027) \" double quote (\u0022) 19

20 Literals Integer literals An integer literal is of type long if it ends with the letter L or l; otherwise it is of type int. It is recommended that you use the upper case letter L because the lower case letter l is hard to distinguish from the digit 1. Values of the integral types byte, short, int, and long can be created from int literals. Values of type long that exceed the range of int can be created from long literals. 20

21 Literals Integer literals (cont d) 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 0x or 0X 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 x1D 0X1d 21

22 Literals Floating-point literals A floating-point literal is of type float if it ends with the letter F or f; otherwise its type is double and it can optionally end with the letter D or d. The floating point types (float and double) can also be expressed using E or e (for scientific notation), F or f (32-bit float literal) and D or d (64- bit double literal; this is the default and by convention is omitted). 22

23 Literals Floating-point literals (cont d) 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: e1.18E e-1 23

24 Literals Floating-point literals (continued) The hexadecimal form consists of 0x (or 0X), 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): 0x12p0 0x1.2p4 0x.12P+8 0x120p-4 24

25 Literals Floating-point literals (continued) 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. 25

26 Literals String literals (continued) String literals appear with double quotes, e.g. Welcome, salam, "\u0633\u064e\u0644\u064e\u0627\u0645\u064c". 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. 26