การโปรแกรมเชิงวัตถุด้วยภาษา JAVA

1. การโปรแกรมเชิงวัตถุด้วยภาษา JAVA Keyword & Data Type มหาวิทยาลัยเนชั่น http://www.nation.ac.th บุรินทร์ รุจจนพันธุ์ . ปรับปรุง 15 มิถุนายน 2552

2. 49 Java Keywords (Sorting) abstract boolean break byte case catch char class const continue default do double else extends final finally float for goto if implements import instanceof int interface long native new package private protected public return short static strictfp super switch synchronized this throw throws transient try void volatile while assert

3. 49 Java Keywords (4 Groups) DATA boolean byte char double final float int long short static strictfp transient void CONTROL assert break case catch continue default do else finally for if return switch synchronized throw throws try while OBJECTS abstract class extends implements import instanceof interface native new package private protected public super this volatile Unused const goto

4. 49 Java Keywords (9 Groups 1/5) 1. Access Modifiersprivate : Makes a method or a variable accessible only from within its own class. protected : Makes a method or a variable accessible only to classes in the same package or subclasses of the class. public : Makes a class, method, or variable accessible from any other class.

5. 49 Java Keywords (9 Groups 2/5) 2. Class, Method, and Variable Modifiersabstract : Used to declare a class that cannot be instantiated, or a method that must be implemented by a nonabstract subclass. class : Keyword used to specify a class. extends : Used to indicate the superclass that a subclass is extending. final : Makes it impossible to extend a class, override a method, or reinitialize a variable. implements : Used to indicate the interfaces that a class will implement. interface : Keyword used to specify an interface. native : Indicates a method is written in a platform-dependent language, such as C. new : Used to instantiate an object by invoking the constructor. static : Makes a method or a variable belong to a class as opposed to an instance. strictfp : Used in front of a method or class to indicate that floating-point numbers will follow FP-strict rules in all expressions. synchronized : Indicates that a method can be accessed by only one thread at a time. transient : Prevents fields from ever being serialized. Transient fields are always skipped when objects are serialized. volatile : Indicates a variable may change out of sync because it is used in threads.

6. 49 Java Keywords (9 Groups 3/5) 3. Flow Controlbreak : Exits from the block of code in which it resides. case : Executes a block of code, dependent on what the switch tests for. continue : Stops the rest of the code following this statement from executing in a loop and then begins the next iteration of the loop. default : Executes this block of code if none of the switch-case statements match. do : Executes a block of code one time, then, in conjunction with the while statement, it performs a test to determine whether the block should be executed again. else : Executes an alternate block of code if an if test is false. for : Used to perform a conditional loop for a block of code. if : Used to perform a logical test for true or false. instanceof : Determines whether an object is an instance of a class, superclass, or interface. return : Returns from a method without executing any code that follows the statement (can optionally return a variable). switch : Indicates the variable to be compared with the case statements. while : Executes a block of code repeatedly while a certain condition is true.

7. 49 Java Keywords (9 Groups 4/5) 4. Error Handlingcatch : Declares the block of code used to handle an exception. finally : Block of code, usually following a try-catch statement, which is executed no matter what program flow occurs when dealing with an exception. throw : Used to pass an exception up to the method that called this method. throws : Indicates the method will pass an exception to the method that called it. try : Block of code that will be tried, but which may cause an exception. assert : Evaluates a conditional expression to verify the programmer’s assumption. 5. Package Controlimport : Statement to import packages or classes into code. package : Specifies to which package all classes in a source file belong.

8. 49 Java Keywords (9 Groups 5/5) 6. Primitivesboolean : A value indicating true or false. byte : An 8-bit integer (signed). char : A single Unicode character (16-bit unsigned) double : A 64-bit floating-point number (signed). float : A 32-bit floating-point number (signed). int : A 32-bit integer (signed). long : A 64-bit integer (signed). short : A 16-bit integer (signed). 7. Variable Keywordssuper : Reference variable referring to the immediate superclass. this : Reference variable referring to the current instance of an object. 8. Void Return Type Keywordvoid : Indicates no return type for a method. 9. Unused Reserved Wordsconst : Do not use to declare a constant; use public static final. goto : Not implemented in the Java language. It’s considered harmful.

9. boolean, char, byte, short, int, long // 1. boolean true of false boolean b = true; System.out.println("boolean = "+b); // 2. character (2 Byte) char y; y = 'a'; System.out.println("character = "+y); // 3. byte -2^7 to 2^7-1 (1 Byte) byte c; c = 127; System.out.println("byte = "+c); // 4. short -2^15 to 2^15-1 (2 Byte) short a; a = 32767; System.out.println("Short = "+a); // 5. integer -2^31 to 2^31-1 (4 Byte) int x; x = 2147483647; System.out.println("Integer = "+x); // 6. long -2^63 to 2^63-1 (8 Byte) long b; b = 9223372036854775807L; System.out.println("long = "+b);

10. float, double // 7. float -3.4e38 to 3.4e38 (4 Byte) float d; d = 340000000000000000000000000000000000000f; System.out.println("float = "+d); // 8. double -1.7e308 to 1.7e308 (8 Byte) double e; e = 17900000000000000000000000000000000000000d; System.out.println("double = "+e);

11. Literals & Casting float f = 1.0f, 1.0F double d = 1.0, 1.0f boolean b = true, false char c = (char)70000; = 4464 (0-66535) byte b = (byte)300; error on byte b = 300; Hexadecimal Literals 0x001, 0xcafe; error on 0xone, 0xjava Octal Literals 011, 071 error on 081, 099 char c = 'e', '\u0065' (hex) error on '\u065', '\u00065', 'aa', "a"

12. Convert of Number and String String aa = Double.toString(123.45); String bb = Integer.toString(123); double cc = Double.parseDouble("123") + 1; int dd = Integer.parseInt("456") + 2; String xx = Double.toString(Double.parseDouble("123") + 1); String yy = Integer.toString(Integer.parseInt("456") + 2); ข้อมูลจาก http://yn1.yonok.ac.th/burin/javadocs/api/java/lang/String.html

13. String Class String z ="ThaiAll"; System.out.println("string = "+z); System.out.println(z.substring(0,4)); // Thai System.out.println(z.substring(2,5)); // aiA System.out.println(z.substring(4)); // All System.out.println(z.toUpperCase()); // THAIALL System.out.println(z.toLowerCase()); // thaiall char ar[] = new char[128]; ar = z.toCharArray(); System.out.println((char)ar[0]); // T System.out.println(ar[0]); // T System.out.println(ar[2] + ar[4]); // 162 (97+65) ข้อมูลจาก http://yn1.yonok.ac.th/burin/javadocs/api/java/lang/String.html

14. Argument of Main // java j0100 abc def class j0100 { public static void main(String args[]) { System.out.println(args.length); System.out.println(args[0]); // abc } }

15. Data Structure Size TeraByte Database Relation GigaByte Table MegaByte Record KiloByte Field Data Type Byte Character BIT

16. Stack Memory 1 2 c d Stack Memory Heap Memory a = 1 a b 4 4 b = 2 c int a = 1; int b; b = a; a = 2; int c[]={3}; int d[]= c; c[0] = 4; System.out.println(“”+a+b+c[0]+d[0]); d