Skip to main content

Object,Data Hiding

Object:-

Object is real time entity exist in the real world , the basic purpose of object is to transfer data from one location to another location.object is small memory , allocated inside primary memory(RAM).in java object created inside heap memory,actually in java RAM memory  is divided into some segment according to the type of variables for example.

RAM==>Heap area+Stack area+String constant pool+class area  etc.
when object created then inside object only non static class variables occupied memory and initialize with default values.
non static class variables also known as instance variable reside into object in heap area,static variables occupied memory in class area at the time of class loading from HARD disk to RAM and all local variables occupied memory in stack area when reaching to variables.
object  created from the class then what object contains is depend on class structure or class members.

             class Animal
            {

                             
                                      ==================>    cow,goat,.....
         
         
           
           }
         
           logical unit or formula =============>  in the above  cow ,goat,......are exist in      the real words they are objects present in the real world but Animal is a class which is not exist in the real world so from Animal class we can create cow ,goat,...real time objects,that means objects are class type variable.


Data Hiding:-

Data hiding is a concept of providing  security to our data.if we don't want to share our class data to outside class or outside world then this concept is known as data hiding.
for achieving data hiding for class variables we have to declare all the class variables as a private.

 For example :-
                          class Student
                          {
                     private int rollNo;
                     private String name;
                     private String address;
                           }            
                                                   or

                          class Student
                         {
                    private int rollNo;
                    private String name;
                    private String address;
                    public int getRollNo()
                           {
              return rollNo;
                    }
                    public void setRollNo(int rollNo)
                           {
             this.rollNo = rollNo;
                    }
                   public String getName()
                          {
             return name;
                   }
                   public void setName(String name)
                         {
            this.name = name;
                  }
                  public String getAddress()
                         {
           return address;
                  }
                 public void setAddress(String address)
                        {
           this.address = address;
                 }

                     }

in the above class all the data field are declared as private then the above data can not access outside of the class.
it does not matter that the class having method or not but all the data field must be declared with private access modifier.so above class is a example of data hiding.


Comments

Popular posts from this blog

Inner classes

Inner Classes:- class inside class or interface called inner class or nested class. Advantage of inner classes is grouping multiple classes and interfaces into a single class. Another big advantage of inner class is that inner class can happily access all the data or variables of outer class directly. Types of Nested classes:- There are two types of nested classes static and non-static nested classes. (A)Non –static inner classes:- 1)     Member inner class 2)     Anonymous inner class 3)     Local inner class (B)Static nested class Example1:-Outer.java class Outer { class Inner { void disp() { System.out.println("Hello This is Inner class Method"); } } public static void main(String[]args) { Inner in=new Inner(); in.disp(); } } Output:- C:\JAVATECH>javac Outer.java Outer.java:12: error: non-static variable this cannot be referenced from a static context Inner in=new Inner(); ...

Small concept about OOPs

Some small concept about OOPs:- In many books and website write about OOPs concepts as hundred percent object oriented, pure object oriented and partial object oriented language. Hundred percent object oriented:- In the hundred percent object oriented movie hero is object, without object program is incomplete that means can not execute program without object. Without class and object programming or application development is not possible. Example of hundred percent object oriented language is  Smalltalk . Pure object oriented:- In the object oriented cinema obviously object is the hero. In pure object oriented language object having same importance but in this having some relax that is without creating object we can successfully execute our application. So in the object oriented programming without class we cannot create or run our application, class is must. Example of pure object oriented language is  Java . Partial object oriented:- In this type of la...

Inheritance-4

Example10:- class Student { Student() { System.out.println("This is super class Zero argument constructor"); } Student(String s) { System.out.println("This is super class One argument constructor"); } } class Test extends Student { Test() { super(null); System.out.println("This is sub class Zero argument constructor"); } public static void main(String[]args) { Test t=new Test(); } } Output:- C:\JAVATECH>javac Test.java C:\JAVATECH>java Test This is super class One argument constructor This is sub class Zero argument constructor Example11:- class Student { Student() { System.out.println("This is super class Zero argument constructor"); } Student(String s) { System.out.println("This is super class One argument constructor"); } } class Test extends Student { Test() { super(); super(null); System.out.println("This is su...