garbage Collection در جاوا

• JVM does the garbage collection action

چند نکته در مورد Context و Static در جاوا

• static is a keyword.
• context will be created 1 time but object will be created many times.
• context of the class is a memory location present inside RAM.
• context is used to Load static members. the context of the class will be created only one per class.
• JVM creates context of the class.
• basically the members of the context are known as class variables because we can access them using the context name that is same as class name.
• when you give .class file to jvm for execution, jvm loads all the static members and blocks to context of the class.
• JVM first searches for the static block in the context of the class and once the block executions is finished, jvm searches for main method and executes the main method.
• we can create many static block but it is not necessary.
• we can call non static main method in static block. actually after that it is not main method and it can have any other name.
• if we don't create static main method we can not have input parameter from command line
• main method is necessary for C and C++ because they don't support static block but because of static block main method is not necessary in Java

تفاوت های Method و Constructor در جاوا

Differents between Method and Constructor are as follows:

Constructor	Method
does not contain any return type	has a signature of return type, name and the arguments
should be same as class name	method name can not be same as a class name
Constructor can be called only once per object	we can call a method n number of times on a particular object

چند نکته در مورد Constructor در جاوا

• Constructor is same as method without return type. It's job only an  initialization the instance variables with the default values.
• Explicitly we can not call the constructor. JVM has to call the constructor.
• Constructors name should be same as the class name.
• The constructor can be created when the we create the object.
• The constructor can be call only once per object.
• Job of construction: set default value to class variables.
• If we pass argument to constructor it is known as parameter constructor
• We can create our java class without any constructor but a java class without constructor is not possible, because the java compiler adds the default constructor if a user has not mentioned any constructor
• Note**: Java compiler adds default constructor nooooot JVM

data type در جاوا

• Java support 8 different data typs. They are categorized in 4 Groups

• in Logical group Java does not use 0 and 1, Java uses true and false

Integer:default is 0		Real:default is 0.0	Character: default is space	Logical: default is false
Byte (1 byte)		Float (4 byte)	char (2 byte)	boolean (1 bit)
Short (2 byte)		double (8 byte)
Int (4 byte)
long (8 byte)