Java learning Series | Day-2

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