What is the importance of clone() method in Java?

clone() method is used to create a copy of an object of a class that implements the Cloneable interface. By default, it copies on a field-by-field basis because the Object class does not know the members of the specific class whose object calls this method. So if the class only has primitive data type members, a new copy of the object will be created and a reference to the new copy of the object will be returned. However, if the class contains members of any class type, only the object references to those members are copied, so the member references in both the original and cloned objects refer to the same object.

If we try to call the clone() method on an object of a class that does not implement the Cloneable interface, we will receive a CloneNotSupportedException . This interface is a tagged interface, the implementation of which only indicates that the Object.clone() method can be called on an object of the implementing class.

Syntax

<strong>protected Object clone() throws CloneNotSupportedException</strong>

We can implement the clone() method in two ways

Shallow copy

This is provided by Object.clone() The result of the default clone function method (if the class also has non-basic data type members). In the case of shallow copy, the cloned object also refers to the same object that the original object refers to, since only the object reference is copied and not the referenced object.

Example

public class ShallowCopyTest {
   public static void main(String args[]) {
      A a1 = new A();
      A a2 = (A) a1.clone();
      a1.sb.append("Tutorialspoint!");
      System.out.println(a1);
      System.out.println(a2);
   }
}
class A implements Cloneable {
   public StringBuffer sb = new StringBuffer("Welcome to ");
      public String toString() {
         return sb.toString();
      }
   public Object clone() {
      try {
         return super.clone();
      } catch(CloneNotSupportedException e) {
      }
      return null;
   }
}

Output

Welcome to Tutorialspoint!
Welcome to Tutorialspoint!

##Deep Copy

We need classes for non-basic types Override the

clone() method member to implement deep copy because it also requires cloning the member object, which the default cloning mechanism does not do.

Example

public class DeepCopyTest {
   public static void main(String args[]) {
      A a1 = new A();
      A a2 = (A) a1.clone();
      a1.sb.append(" TutorialsPoint!");
      System.out.println(a1);
      System.out.println(a2);
   }
}
class A implements Cloneable {
   public StringBuffer sb = new StringBuffer("Welcome to ");
   public String toString() {
      return sb.toString();
   }
   public Object clone() {
      try {
         A a = (A) super.clone();
         a.sb = new StringBuffer(sb.toString());
         return a;
      }
      catch(CloneNotSupportedException e) {
      }
      return null;
   }
}

Output

Welcome to TutorialsPoint!
Welcome to

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