3.9 Keywords

Keywords are predefined identifiers (name of basic programming elements) which are having a special meaning in java source code. Rule Keywords can’t be used as user defined identifiers, means, can’t be used by the programmer for variable, method, class names because keywords are reserved words. There are 50 keywords are available in java, among them 47 are introduced in java1.0 and 1.1 In java1.2 new keyword strictfp was added In java1.4 new keyword assert was added In java1.5 new keyword enum was added

The following character sequences, formed from ASCII letters, are reserved for

use as keywords and cannot be used as identifiers (§3.8):

The keywords const and goto are reserved, even though they are not currently

used. This may allow a Java compiler to produce better error messages if these C++ keywords incorrectly appear in programs.

While true and false might appear to be keywords, they are technically

Boolean literals (§3.10.3). Similarly,

while null might appear to be a keyword, it is technically the null literal

Note

Below three are Literals not key words

Boolean Literals true , false

Object Literal (default value) null

Note

Keywords should write in lower case. Violation leads to compile time error.

The below are the list of java keywords

Java files	class interface enum(1.5)
data types	byte , short, Int ,long float, double ,char boolean, void
Memory location	static new
Control statements(11) Conditional(5) Loop(3) Transfer(3)	If , else switch, case, default while, do for(; ;) for(:) (1.5) break, continue, return
Access specifier(3)	Private, , protected, public
Access modifiers	static final abstract native transient volatile synchronized strictfp
Inheritance relationships	extends implements
Object relationships	this super instanceof
package	Package Import
Exceptional handling	try, catch, finally throw, throws assert
Reserved keywords	goto const