Java Tokens
Java tokens are the smallest units or elements of a program. We have six main tokens available in Java:
1. Identifiers
Identifiers are generally defined by users. They are used to name a variable, constant, function, class, or array. Underscores, alphabets, or the dollar sign can be used here as the first character. However, we have to always keep in mind that the identifier name must be different from the reserved keywords.
Let’s have a look at the rules to declare identifiers:
- Identifiers are always case-sensitive.
- The first letter of an identifier will always be an alphabet, underscore, or the dollar sign.
- No white spaces are allowed.
Examples of some valid identifiers:
- CarName
- PETROL
- diameter
- i
- a1
- _carname
- $radius
- java_array
Example of an invalid identifier: 13diameter
2. Literals
In Java, literals represent a fixed value in the source code. They are defined by a programmer. Literals in Java once defined cannot be changed. There are five main categories of literals:
- Integer
- Floating point
- String
- Character
- Boolean
| Literal |
Type of Literal |
| 56 |
int |
| 45.65 |
double |
| false, true |
boolean |
| ‘S’, ‘4’, ‘-‘ |
char |
| “Intellipaat” |
string |
| null |
any reference type |
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3. Operators
Operators in Java are the symbols that are used to perform operations on operands. Let’s see the total eight types of operators present in Java as listed below:
- Arithmetic operators
- Assignment operators
- Relational operators
- Logical operators
- Unary operators
- Ternary operators
- Shift operators
- Bitwise operators
| Operators |
Symbols |
| Arithmetic |
+ , – , / , * , % |
| Assignment |
= , += , -= , *= , /= , %= , ^= |
| Relational |
==, != , < , >, <= , >= |
| Logical |
&& , || |
| Unary |
++ , – – , ! |
| Ternary |
(Condition) ? (Statement1) : (Statement2); |
| Shift |
<< , >> , >>> |
| Bitwise |
& , | , ^ , ~ |
4. Separators:
Separators are punctuators present in Java. Let’s look at some of the useful separators in Java:
- Period (.): It is used to separate the package name from the sub-packages and the class. Also, it is used to separate a variable or method from a reference variable.
- Comma (,): It is basically used to separate two values, statements, and parameters.
- Parentheses (): We use it to call functions and parse the parameters.
- Curly braces {}: Whenever we want to start or end a block of code, we use curly braces.
- Assignment operator (=): We use it to assign a variable and a constant.
- Semicolon (;): It separates the two statements of the code.
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5. Keywords
Keywords are the reserved words in Java. Each of their meaning is already known to the compiler. Let’s look at the Java keywords given in the below table:
| case |
boolean |
char |
continue |
class |
| abstract |
catch |
byte |
default |
break |
| do |
double |
else |
extends |
final |
| finally |
float |
int |
if |
implements |
| import |
instanceof |
for |
interface |
long |
| native |
new |
package |
private |
protected |
| public |
return |
short |
static |
super |
| switch |
synchronized |
this |
thro |
throws |
| transient |
void |
try |
while |
volatile |
| assert |
enum |
const |
strictfp |
goto |
Let’s learn about some of these keywords further:
- case: It is used with the switch statements to mark the blocks of text.
- catch: It is used to catch the exceptions generated by try statements. We can only use it after a try block.
- char: It is used to declare a variable that can hold unsigned 16-bit Unicode characters.
- class: It is used to declare a class.
6. Comments
Comments are used to give a description of the Java code. There are mainly two types of Java comments available as listed below:
- Block-oriented: It is a multi-line comment that starts with /* and ends with */. It can have multiple rows.
- Line-oriented: It is a single-line comment and starts with //.