Object Cloning In Java | Java Object Clone Without Cloneable

 Object Cloning in Java

The object cloning is a way to create exact copy of an object. The clone() method of Object class is used to clone an object.

The java.lang.Cloneable interface must be implemented by the class whose object clone we want to create. If we don't implement Cloneable interface, clone() method generates CloneNotSupportedException.

The clone() method is defined in the Object class.

Fig: Object Cloning

Syntax:

protected Object clone() throws CloneNotSupportedException  

Advantage of Object cloning:

Although Object.clone() has some design issues but it is still a popular and easy way of copying objects. 

Following is a list of advantages of using clone() method:

• You don't need to write lengthy and repetitive codes. Just use an abstract class with a 4- or 5-line long clone() method.
• It is the easiest and most efficient way for copying objects, especially if we are applying it to an already developed or an old project. Just define a parent class, implement Cloneable in it, provide the definition of the clone() method and the task will be done.
• Clone() is the fastest way to copy array.

Disadvantage of Object cloning:

Following is a list of some disadvantages of clone() method:

• To use the Object.clone() method, we have to change a lot of syntaxes to our code, like implementing a Cloneable interface, defining the clone() method and handling CloneNotSupportedException, and finally, calling Object.clone() etc.
• We have to implement cloneable interface while it doesn't have any methods in it. We just have to use it to tell the JVM that we can perform clone() on our object.
• Object.clone() is protected, so we have to provide our own clone() and indirectly call Object.clone() from it.
• Object.clone() doesn't invoke any constructor so we don't have any control over object construction.
• If you want to write a clone method in a child class then all of its superclasses should define the clone() method in them or inherit it from another parent class. Otherwise, the super.clone() chain will fail.
• Object.clone() supports only shallow copying but we will need to override it if we need deep cloning.

Example of Object cloning

   class Student implements Cloneable{  

   int rollno;  

   String name;  

     

   Student(int rollno,String name){   

   this.rollno=rollno;  

   this.name=name;   

    }  

          

   public Object clone()throws CloneNotSupportedException{  

   return super.clone();  

    }  

          

   public static void main(String args[]){  

   try{  

  Student s1=new Student(101,"pramod");  

     

   Student s2=(Student)s1.clone();  

  

   System.out.println(s1.rollno+" "+s1.name);  

   System.out.println(s2.rollno+" "+s2.name);  

  

}  catch(CloneNotSupportedException c){}  

   Output:

          101 pramod

          101 pramod