Java Create Object in 5 ways

BySimple App
September 29, 2023
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1. Using a new keyword.

– It’s the most popular one. We create an object by using a new operator followed by a constructor call.

Exemple :

class ClassA{
}ClassA obj = new ClassA()

2. newinstance() method

– Using the newInstance() method of class “Class”

Exemple :

class ClassA {
}
ClassA obj = ClassA.class.newInstance();

3. newinstance() method – 2

– Using the newInstance() method in class “Constructor”.

Exemple :

class ClassA {
}Constructor<ClassA> obj = ClassA.class.getConstructor().newInstance();

– Both the previous ways (Shown in 2 and 3), are known as reflective ways of creating objects.

Fun-fact:

– Class’s newInstance() method internally uses Constructor’s newInstance() method.

4. clone method

– Using “Object” class clone() method. The clone() method creates a copy of an existing object.

– The clone) method is part of the “Object” class which returns a clone object.

– Example:

public class ClassA implements Cloneable {
protected Object clone() throws CloneNotSupportedException {//.....}}
ClassA obj1 = new ClassA( );
ClassA obj2 = (ClassA)obj1.clone();

– Always Remember:

The “Cloneable” interface is implemented.
The clone() method must be overridden with other classes.
Inside the clonel() method, the class must call super.clone().

Learn more : Cloning in Java: Understanding Shallow Copy and Deep Copy

5. Deserialization

– When we deserialize any object then JVM creates a new object internally.

For this, we need to implement the Serializable interface.

– Example:

import java.io.*;

public class ClassA implements Serializable {
    // Attributs et méthodes de la classe
}

public class SerializationExample {

    public static void main(String[] args) {
        // Création d'un objet pour la sérialisation
        ClassA classA = new ClassA();

        // Sérialisation
        try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("class.obj"))) {
            out.writeObject(classA);
        } catch (IOException e) {
            e.printStackTrace();
        }

        // Désérialisation
        ClassA deserialClassA = null;
        try (ObjectInputStream in = new ObjectInputStream(new FileInputStream("class.obj"))) {
            deserialClassA = (ClassA) in.readObject();
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}