Whitespace

Java is a free-form language. This means that you do not need to follow any special indentation rules. For instance, the Example program could have been written all on one line or in any other strange way you felt like typing it, as long as there was at least one whitespace character between each token that was not already delineated by an operator or separator. In Java, whitespace is a space, tab, or newline.

Identifiers

Identifiers are used for class names, method names, and variable names. An identifier may be any descriptive sequence of uppercase and lowercase letters, numbers, or the underscore and dollar-sign characters. They must not begin with a number, lest they be confused with a numeric literal. Again, Java is case-sensitive, so VALUE is a different identifier than Value.

int temperature = 35; // temperature is an identifier

Literals

A constant value in Java is created by using a literal representation of it.

int temperature = 35; // 35 is a literal

Comments

Single Line Comments

int temperature = 35; // this is single line comment

Multiple Line Comments

int temperature = 35; /* this is
a multiline
comment*/
int humidity = 80;

Java Keywords

Java Keywords are the reserved words that you cannot use as Identifiers in your program. every program uses some of these keywords so that compiler understand what is declared and defined in program. The keywords are as follows :-

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