24 How to create Object using clone() method in java?

Clone: Cloning  means creating new object with the existing object state is called as cloning.

Simple Program to understand why cloning is required:

A.java

class A
{
int a = 111;
int b = 222;

public static void main( String[] clone )
{
A obj = new A();
System.out.println(" obj: "+obj.a+"..."+obj.b);

A obj1 = obj;
System.out.println(" obj1: "+obj1.a+"..."+obj1.b);
System.out.println(" obj: "+obj.hashCode() );
System.out.println(" obj1: "+obj1.hashCode() );
}
}

Output:  

Program For Clonning

B.java

class B implements Cloneable
{
  int a = 111;
int b = 222;

public static void main( String[] s)
throws CloneNotSupportedException{
B obj = new B();
System.out.println(" obj: " + obj.a +"..."+obj.b);

obj.a = 888;
obj.b = 999;
System.out.println(" obj: " + obj.a +"..."+obj.b);

B obj1 = new B();
System.out.println(" obj1: " + obj1.a +"..."+obj1.b);

Object o = obj.clone();
B obj2 = (B)o; // DownCasting
System.out.println(" obj2: " + obj2.a +"..."+obj2.b);

System.out.println("\n\n obj: "+obj.hashCode());
System.out.println(" obj1: "+obj1.hashCode());
System.out.println(" obj2: "+obj2.hashCode());
}
}

Output:  

Shallow Clonning

Student.java

class Address{
String cityName = "Hyderabad";
String stateName = "Telangana";
}

class Student implements Cloneable{
int sid = 101;
String sname = "ram";
int sage = 29;

Address addr = new Address();

public static void main( String args[] )
throws CloneNotSupportedException{

Student s1 = new Student();

System.out.println( s1.sid );
System.out.println( s1.sname );
System.out.println( s1.sage );
System.out.println( s1.addr.cityName );
System.out.println( s1.addr.stateName );

s1.sid = 111;
s1.sname = "Atharva";
s1.sage  = 30;
s1.addr.cityName = "Dhule";
s1.addr.stateName = "Maharashtra";

System.out.println("---------S1 Details-----------");
System.out.println( s1.sid );
System.out.println( s1.sname );
System.out.println( s1.sage );
System.out.println( s1.addr.cityName );
System.out.println( s1.addr.stateName );

Student s2 = (Student)s1.clone();

System.out.println("---------S2 Details-----------");
System.out.println( s2.sid );
System.out.println( s2.sname );
System.out.println( s2.sage );
System.out.println( s2.addr.cityName );
System.out.println( s2.addr.stateName );

System.out.println("\n\n"+s1.hashCode()+"     "+s2.hashCode());

// If address of anyone memory location got change then it will reflect
// to both.

s1.addr.cityName = "chennai";
System.out.println( s1.addr.cityName );
System.out.println( s2.addr.cityName );

}
}

Output:  

Deep Clonning

Student.java

class Address extends java.lang.Object implements Cloneable{
String cityName = "Hyderabad";
String stateName = "Telangana";

public Address clone() throws CloneNotSupportedException{
return (Address)super.clone();
}
}

class Student extends java.lang.Object implements Cloneable{
int sid = 101;
String sname = "ram";

Address addr = new Address();

public Student clone() throws CloneNotSupportedException
{
Student s3 = (Student) super.clone();
s3.addr = this.addr.clone();

return s3;
}

public static void main( String args[] )
throws CloneNotSupportedException{

Student s1 = new Student();
Student s2 = s1.clone();

System.out.println("\n\n S1: \n"+s1.sid );
System.out.println( s1.sname );
System.out.println( s1.addr.cityName );
System.out.println( s1.addr.stateName );

System.out.println("\n\n S2: \n"+s2.sid );
System.out.println( s2.sname );
System.out.println( s2.addr.cityName );
System.out.println( s2.addr.stateName );

s2.addr.cityName = " Dhule ";
s2.addr.stateName = " Maharashtra ";

System.out.println("\n\n S1: " + s1.addr.cityName );
System.out.println( s1.addr.stateName );

System.out.println("\n\n S2: " + s2.addr.cityName );
System.out.println( s2.addr.stateName );

}
}

Output:  

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