Ajay

Posted on Oct 29

Java learning Series | Day-2

#java #webdev #backend #fullstack

What is data Type ?

Java is a statically type language , means every variable must be declared with a specific data type before it can be used.

int age = 10;
String name = "ajay"

Data types are divided into,

1) Primitive data type,
2) Non-primitive data type.

1) Primitive data type:

Primitive data type specifies the type of the variable and store the value

Number:

byte(8 bit)--> Stores the whole number from -128 to 127 (2**8 = 256)
short(16 bit)---> Stores whole numbers from -32,768 to 32,767 (2**16 = 65,536)
int(32-bit)---> stores whole number from -2,147,483,648 to 2,147,483,647 (2**32 = 4,294,967,296)
long(64 bit)--->Stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 (2**64 = 18,446,744,073,709,551,616)

Decimal number :

float(32 bit) --->Single-precision decimal. Requires an f suffix.Sufficient for storing 6 to 7 decimal digits
double(64 bit) --->Double-precision decimal (default for decimals). Sufficient for storing 15 to 16 decimal digits
boolean(8 bit)---> the boolean data type has two possible value : True or False , bascially used for logical condition.
char(16 bit) --->Stores a single character/letter or ASCII values

Default value for primitive data type

2) Non-Primitive data type:

Non-primitive data type are created by programmer,Instead of storing actual value its stores memory references,
Non-primitive types can be used to call methods to perform certain operations

String --> A sequence of characted wrapped in double quotes.

String name = "Ajay";

Array ---> Array are used to stored multiple value in a single variable,To declare an array the variable type should defined by square brackets [].

String [] cars = { "audi", "BMW", "BenZ"}
int[] myNum = {10, 20, 30, 40};

Class and object Enverthing in the java is associated with class and object Class Class like an object contructor , a template or blueprint for creating object.

Create a Class

create a class using class keyword,
Rule of creating Class name

class name should first with upper case,
should br meaning full name,
No space allowed,
should be in upperCase or camelCase,
Special Charactors only "_" and "$" is allowed.

public class Main{
}
public class SuperMarket{
}
public class Super_Market{
}
public class Super$Market{
}

Creat a object

Object is created only inside the class.
Using new Keyword a object is created.

public class Main{
public Static void main(String[] args){
Main myObject = new Main();
}
}

Default value for Non-primitive data type

Default value is always null for all type in non-primitve type

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