Regarding tokens

1. Java Tokens: Keywords, Identifiers, Literals, Operators, and Seperators

2. A smallest individual unit in source code is known as Token
Java Tokens
Keywords Identifiers Literals Operators Seperators

3. Keywords are special tokens in the language which have reserved use in the language.
Keywords may not be used as identifiers in Java — you cannot declare a field whose name is a
keyword, for instance.
Java has 50 keywords among which 48 are in use but 2 (goto and const) are currently not in use
Here is a list of keywords in the Java programming language. You cannot use any of the
following as identifiers in your programs. The keywords const and goto are reserved, even
though they are not currently used. true, false, and null might seem like keywords, but they are
actually literals; you cannot use them as identifiers in your programs.
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
* not used
** added in
1.2
*** added in
1.4
**** added in
5.0

4. Identifiers are the names of variables, methods, classes, packages and interfaces.
• Don’t use a keyword
• Don’t use a space
• Don’t use a special symbol other than ( _ and $ )
• Cannot start with digit
• Any length
• If only a single word then use a lowercase
• If more than one word then start first word with lowercase and other words start with first
letter as Capital
For example:
int balance=500; //Single word
int bankBalance=500; //Multiple Words

5. • Use lowercase
For example:
package pack1;
package mypack1;
• Every word start with first letter as Capital
For example:
class Balance{}
class BankBalance{}
• Use Uppercase and Underscore for separating the words
For example:
int PI=3.14;
int MAX_VALUE=100;

6. Fixed value assigned to variables or used in expressions is known as Literals
• Integer Literals: for example: 1, -2, 8523, -2105 etc.
Data Type Size Range
byte 1 Byte -27 to 27 -1
short 2 Bytes -215 to 215 -1
int 4 Bytes -231 to 231 -1
long 8 Bytes -263 to 263 -1
• Floating Literals: for example: 1.02, -2.689, 8523.369, 2105 etc.
Data Type Size Range
float 4 Byte -3.4 * 1038 to 3.4 * 1038
double 8 Bytes -1.7 * 10308 to 1.7 * 10308

7. • Character Literals: for example: ‘A’, ‘B’, ‘@’, ‘&’ etc.
Data Type Size Range
char 2 Bytes All Unicode characters
• String Literals: for example: “Hello”, “Gurpreet Singh”, “ACET” etc.
Data Type Size Range
String 2 * No. of characters As much memory available
• Boolean Literals: true and false.
Data Type Size Range
boolean 1 Byte true or false
• Null Literals: null can be assigned to any reference type

8. Operators operates on operands. For example: In expression a+b , a & b are operands and +
is operator
• Arithmetic Operator: +, - , *, /, %. For example:
5+4 will result in 9 5-4 will result in 1 5*4 will result in 20 5/4 will result in 1
5%4 will result in 1 (remainder) -5%4 will result in -1 5%-4 will result in 1 -5%-4 will result in -1
Note: Sign of result in % operator depends on the sign of dividend(numerator)
• Relational Operator: <, >, <=, >=, ==, != Output will be either true or false
5>6 will result in false
5>=6 will result in false (either greater than or equal to)
5<6 will result in true
5<=6 will result in true (either less than or equal to)
5==6 will result in false (equal to)
5!=6 will result in true (not equal to)

9. • Assignment Operator: = Assign the value on left hand side to right hand side. For example:
A=10+5, will assign 15 to A
• Logical Operator: returns true or false
Logical AND (&&)
Logical OR (||)
Logical NOT (!)
A B A&&B A||B !A
true true true true false
true false false true false
false true false true true
false false false false true
• Increment/Decrement Operator: increases or decreases the value by 1
Pre-increment & Pre-decrement: ++a, --a
Post-increment & Post-decrement: a++, a--

10. • Bitwise Operator: Performs operations on bits
Bitwise AND(&)
Bitwise OR(|)
Bitwise XOR(^)
Bitwise Complement or Not (!)
A B A&B A|B A^B !A
0 0 0 0 1 1
0 1 0 1 0 1
1 0 0 1 0 0
1 1 1 1 1 0
• Shift Operator: shift the bits to left or right
Left Shift(<<): shifts the bits to left and fill the vacant spaces with 0
Unsigned Right Shift(>>>): shifts the bits to right and fill the vacant spaces with 0
Signed Right Shift(>>): shifts the bits to right and fill the vacant spaces with leftmost bit, i.e. if
leftmost bit is 0 then fill with 0, and if the leftmost bit is 1 then fill with 1
• Conditional(Ternary) Operator:
Syntax: condition(relational expression) ? Expression 1 : Expression 2
If condition evaluates to true then result will be Expression 1 otherwise Expression 2

11. { } used to define block or to declare array with static elements
[ ] used to declare array variable
( ) used to define/call function or used in expressions
; used to terminate a statement
, used to separate variables in declaration
. used to access data members and member functions of an object or class