Java Variables and Literals

int speedLimit = 80;

int speedLimit;
speedLimit = 80;

int speedLimit = 80;
... .. ...
speedLimit = 90; 

int speedLimit = 80;
... .. ...
float speedLimit;

int age = 24;
int AGE = 25;

System.out.println(age);  // prints 24
System.out.println(AGE);  // prints 25

int age;  // valid name and good practice
int _age;  // valid but bad practice
int $age;  // valid but bad practice

int 1age;  // invalid variables

int my age;  // invalid variables

int a = 1;
float b = 2.5;
char c = 'F';

Integer Literals

Integer literals are numeric values (associated with numbers) without any fractional or exponential part. There are 4 types of integer literals in Java:

1. binary (base 2)
2. decimal (base 10)
3. octal (base 8)
4. hexadecimal (base 16)

For example:

// binary
int binaryNumber = 0b10010;
// octal 
int octalNumber = 027;

// decimal
int decNumber = 34;

// hexadecimal 
int hexNumber = 0x2F; // 0x represents hexadecimal
// binary
int binNumber = 0b10010; // 0b represents binary

In Java, binary starts with 0b, octal starts with 0, and hexadecimal starts with 0x.

Note: Integer literals are used to initialize variables of integer types like byte, short, int, and long.

Floating-point Literals

Floating-point literals are numeric literals that have either a fractional form or an exponential form. For example,

class Main {
  public static void main(String[] args) {
    	
    double myDouble = 3.4;
    float myFloat = 3.4F;
 
    // 3.445*10^2
    double myDoubleScientific = 3.445e2;

    System.out.println(myDouble);  // prints 3.4
    System.out.println(myFloat);    // prints 3.4
    System.out.println(myDoubleScientific);   // prints 344.5
  }
}

Note: The floating-point literals are used to initialize float and double type variables.

Character Literals

Character literals are unicode characters enclosed inside single quotes. For example,

char letter = 'a';

Here, a is the character literal.

We can also use escape sequences as character literals. For example, \b (backspace), \t (tab), \n (new line), etc.

String Literals

A string literal is a sequence of characters enclosed inside double-quotes. For example,

String str1 = "Java Programming";
String str2 = "Programiz";

Here, Java Programming and Programiz are two string literals.

Boolean Literals

In Java, boolean literals are used to initialize boolean data types. They can store two values: true and false. For example,

boolean flag1 = false;
boolean flag2 = true;

Here, false and true are two boolean literals