• Friday, November 11, 2016

    8. Java - Java Modifiers

    Java Modifiers Tree

    What is Java Modifier?

    Java Modifier is a keyword used for changing the behavior of variable or class in term of its usage.
    Java Modifier is categorized in two parts:-

    1. Access Modifier
    2. Non Access Modifier 

    How can we use a modifier?

    Simple usage of modifier:

    modifier variableName;

    where modifier is a keyword i.e. public, private, protected, static, final etc...


    What is Java Access Modifier?

    Java Access Modifier is like a security key which gives different access to classes, variables, methods or constructor .  In simple word, it controls the access level and it use for security reason.
    The four Java Access Modifier are:
    1. default :-> It gives access to package (no need to write it).
    2. public :-> Give access to the world.
    3. private :-> Give access to the class only.
    4. protected :-> Give access to package and all sub classes.
    Example:


    //This class can be used by the world.
    public class Test{
       private int myInt; //this variable only access by class Test.
       public String myString; //this variable access by everyone.
       protected int count; //this variable can access in class and sub class.

       private void myMethod(){
        
       }
    }


    What is Java Non Access Modifier?

    Java Non Access Modifier provide various functionality and they are as follows:
    1. static :-> this modifier allows direct access to method and variable without creating an object for its class.
    2. final :-> this modifier affect class, method and variable too in following ways:
      1. A class cannot be subclassed by using final modifier.
      2. A method cannot be override with its sub class.
      3. A variable cannot change its value one initialized.
    3. abstract :-> it use for creating abstract class or method. It means if a class is abstract then it can't be use as a object. It only work as a parent class and it's subclass must have to complete its abstract methods.
      Example:

      abstract class A{
          ......
          ......
          public abstract void myMethod();
      }

      class B extends A{
          ......
          ......
          @Override    public void myMethod(){
             .....
             .....
          }
      }
    4. synchronized :->this modifier used in thread, so we can discuss in Thread tutorial.
    5. volatile :-> this modifier also used in thread.
    Some important information: 
    1. We can use  1 Access Modifier with  1 or more Non-Access Modifier for same variable/class/method.
    2. We cannot use abstract and final same time.
    3. We cannot use private with abstract.

    Syed Masoom Rizvi

    Author & Editor

    Hi, This is Syed Masoom Rizvi, who is continue exploring the world of programming ,programming and programming... :)

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