java - Object, class, datatypes, Access specifiers

Object Oriented Programming:

 To Represent the real world into the computer for solving problems

To simulate the real world into the computer for solving problems

what is object?

• Object is real world entity.
• Combination of state & structure or property & behavior
• Property - Variables - used to identify
• Behavior - methods/functions - used by other object
• Object is an instance of a class.

How to create object:

1. class name
2. followed by object name
3. equal to
4. new keyword
5. then constructor calling

This is a simple object++>

class A{

   A a1=new A();

}

what is class?

collection of objects
Collection of state & behavior
it's a PLAN, BLUEPRINT, TEMPLATE

ex: Tree is class, inside the mangos are object.

Data Types:

Data types are useful to allocate memory for the data whatever I store.
the computer memory is limited so we need use properly.

Primitive data - Fixed in size.

• byte - Stores whole number from (-128 to 127)
• Short - Stores whole number from (-36768 to 32767)
• int - Stores whole numbers from (-2,147,483,648 to 2,147,483,647)
• long - Stores whole numbers from (-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807)
• float - Stores fractional numbers (6 to 7 decimal digits)
• double - Stores fractional numbers (15 decimal digits)
• char - Stores single character/letter or ASCII values.
• Boolean - Stores true or false values

Non primitive data - variable in size (Array, string, class)

For More

Access Specifiers:

• public - access anywhere
• private - access only within the class
• protected - access only child class
• default