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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.


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