คำสงวน (Reserved Word or Java Keywords)
The following character sequences, formed from ASCII letters, are reserved for use as keywords and cannot be used as identifiers. 1. แบบเรียงอักษร : 49 Java Keywords
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
2. แบบแยกกลุ่มใหญ่
DATA
1. boolean
2. byte
3. char
4. double
5. final
6. float
7. int
8. long
9. short
10. static
11. strictfp
12. transient
13. void
CONTROL
1. assert
2. break
3. case
4. catch
5. continue
6. default
7. do
8. else
9. finally
10. for
11. if
12. return
13. switch
14. synchronized
15. throw
16. throws
17. try
18. while
OBJECTS
1. abstract
2. class
3. extends
4. implements
5. import
6. instanceof
7. interface
8. native
9. new
10. package
11. private
12. protected
13. public
14. super
15. this
16. volatile
Unused
1. const
2. goto
3. แบบแยกกลุ่มย่อย (9 กลุ่ม = 49 keywords) 1. Access Modifiers private : 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. 2. Class, Method, and Variable Modifiers abstract : 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. 3. Flow Control break : 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. 4. Error Handling catch : 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 Control import : Statement to import packages or classes into code. package : Specifies to which package all classes in a source file belong. 6. Primitives boolean : 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 Keywords super : Reference variable referring to the immediate superclass. this : Reference variable referring to the current instance of an object. 8. Void Return Type Keyword void : Indicates no return type for a method. 9. Unused Reserved Words const : Do not use to declare a constant; use public static final. goto : Not implemented in the Java language. It’s considered harmful.
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