What is the clone method in Java?

Imagine that you've created an object in Java, complete with all its member functions and data members. Now, you are faced with a dilemma. You need an exact copy of this object, with all its properties intact, but you do not want to waste precious time and effort rewriting the entire code from scratch. That's where the clone() method in Java swoops in and saves the day!

The clone() method in Java is a part of the Cloneable interface and is used to create a copy, or clone, of an object. It provides a convenient way to duplicate an object's state without the need for manual field-by-field copying.

Syntax

protected Object clone() throws CloneNotSupportedException
clone() method syntax

Parameters

The clone() does not take parameters.

Return Type

  • The clone() method in Java returns a copy of the object.

  • If the object does not implement the Cloneable interface, it will throw CloneNotSupportedException .

  • Additionally, since the clone method is protected, it needs to be overridden in order to use it.

Example

Here's an example code snippet that demonstrates the usage of the clone() method 

class Person implements Cloneable {
    private String name;
    private int age;
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    // copy using clone() method
    public Person clone() throws CloneNotSupportedException {
        return (Person) super.clone();
    }
    /**
     * Get the name of the person.
     *
     * @return The name of the person.
     */
    public String getName() {
        return name;
    }
    /**
     * Get the age of the person.
     *
     * @return The age of the person.
     */
    public int getAge() {
        return age;
    }
    public static void main(String[] args) {
        Person person1 = new Person("Alice", 25);
        try {
            // Cloning the person object
            Person person2 = person1.clone();
            // Modifying the cloned object's fields
            person2.name = "Bob";
            person2.age = 30;
            // Outputting the state of both objects
            System.out.println("Person 1 - Name: " + person1.getName() + ", Age: " + person1.getAge());
            System.out.println("Person 2 - Name: " + person2.getName() + ", Age: " + person2.getAge());
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
    }
}

Explanation

  • Lines 1–3: The Person class is defined and implements the Cloneable interface for object cloning. It contains private fields name and age.

  • Lines 5–8: The constructor initializes the name and age fields when a Person object is created.

  • Lines 11–13: The clone() method overrides the Object class's clone() method to enable cloning of Person objects. It performs a copy using super.clone().

  • Lines 20–22: The getName() method returns the name field value.

  • Lines 29–31: The getAge() method returns the age field value.

  • Lines 33–49: In the main() method, a Person object named person1 is created with the name Alice and age 25. It is then cloned to person2 using the clone() method. The name and age fields of person2 are modified to Bob and 30, respectively. The states of both objects are printed to the console.

Advantages of the clone()method

  • It allows two objects to exist independently, despite being copies of one another.

  • Cloning is the fastest way to copy objects.

  • Copy constructor copies all the data over explicitly. However, cloning copies data automatically.

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