Basic modifiers you should know before programming in Java

The static keyword can be used in 4 scenarios

1) static variables

• It is a variable which belongs to the class and not to object(instance)
• Static variables are initialized only once , at the start of the execution . These variables will be initialized first, before the initialization of any instance variables
• A single copy to be shared by all instances of the class
• A static variable can be accessed directly by the class name and doesn’t need any object
• Syntax : <class-name>.

2) static methods

• It is a method which belongs to the class and not to the object(instance)
• A static method can access only static data. It can not access non-static data (instance variables)
• A static method can call only other static methods and can not call a non-static method from it.
• A static method can be accessed directly by the class name and doesn’t need any object
• Syntax : <class-name>.
• A static method cannot refer to "this" or "super" keywords in anyway

3) static blocks of code.

The static block, is a block of statement inside a Java class that will be executed when a class is first loaded in to the JVM

class Test{

static {

//Code goes here

}

}

4) static Inner class.

Make an inner class top-level class

• 
  

The final keyword can be used in 4 scenarios

1) final variables

• It is a variable which can not change its value

2) final method

• It is a method which can not be overriden and dinamically looked up (Polymorphism)

3) final field

• It is a variable which can not change its value. Static final fields are compile-time constants.

4) final class

• It is a calss which can not be subclassed

Modifiers keyword for access levels

Access Levels

	Class	Package	Subclass	World
public	Y	Y	Y	Y
protected	Y	Y	Y	N
no modifier	Y	Y	N	N
private	Y	N	N	N

The transient keyword can be used for a field

1) transient field

• It is a field to not to be serialized with the object serialization.

The synchronized keyword can be used for a method

1) synchronized method

• For a static method, a lock for the class is acquired before executing the method. For a non-static method, a lock for the specific object instance is acquired.

The native keyword can be used for a method

1) native method

• It is a method witch is platform-dependent. It doesn't have body, only signature.