Java Program to Determine the class of an Object

May 25, 2023

What is class in Java ?

In Java, a class is a blueprint for creating objects (a particular data structure), providing initial values for state (member variables or instance variables) and implementations of behavior (member functions or methods).

Classes define objects and the methods that can be used on or by that object. Objects are instances of a class, and they can contain data and methods that operate on that data.

What is Object in Java ?

An object in Java is an instance of a class. It is a unique entity that represents the class and contains its own state and behavior. The state of an object is represented by the values of its instance variables and the behavior of an object is represented by its methods.

An object is created from a class, and you can create multiple objects from a single class. Each object created from a class is unique and operates independently from any other object created from the same class.

Sysntax :

Car myCar = new Car("Toyota", "Camry", 2020);

Ways to Determine the class of Object :

1. instanceof operator: The instanceof operator is used to determine whether an object is an instance of a particular class or an instance of a subclass of that class.

2. getClass() method: The getClass() method is a method defined in the Object class, which is the parent class of all classes in Java. This method returns the Class object that represents the class of the object on which it is called.

3. Class.forName() method: The forName() method of the Class class is used to determine the class of an object based on its fully qualified name.

4. toString() method: The toString() method of the Object class returns a string representation of an object. The string representation of an object includes the name of its class.

Example : using instanceof operator

Run

class Car {
  private String make;
  private String model;
  private int year;

  public Car(String make, String model, int year) {
    this.make = make;
    this.model = model;
    this.year = year;
  }

  public String getMake() {
    return make;
  }

  public String getModel() {
    return model;
  }

  public int getYear() {
    return year;
  }
}

class Main {
  public static void main(String[] args) {
    Car myCar = new Car("Toyota", "Camry", 2020);

    if (myCar instanceof Car) {
      System.out.println("myCar is an instance of Car.");
    } else {
      System.out.println("myCar is not an instance of Car.");
    }
  }
}

Output :

myCar is an instance of Car.

Explanation : In this example, we create an object of the Car class and store it in the myCar variable. Then, we use the instanceof operator to check if myCar is an instance of the Car class. If it is, we print a message indicating that myCar is an instance of Car. If it's not, we print a different message indicating that it's not an instance of Car.

Example : using getClass() Method

Run

class Car {
  private String make;
  private String model;
  private int year;

  public Car(String make, String model, int year) {
    this.make = make;
    this.model = model;
    this.year = year;
  }

  public String getMake() {
    return make;
  }

  public String getModel() {
    return model;
  }

  public int getYear() {
    return year;
  }
}

class Main {
  public static void main(String[] args) {
    Car myCar = new Car("Toyota", "Camry", 2020);

    Class carClass = myCar.getClass();
    System.out.println("The class of myCar is: " + carClass.getName());
  }
}

Output :

The class of myCar is: Car

Explanation : In this example, we create an object of the Car class and store it in the myCar variable. Then, we use the getClass() method to get the Class object that represents the class of the myCar object. Finally, we use the getName() method of the Class class to get the fully qualified name of the class and print it to the console.

Example : Using Class.forName() method

Run

class Car {
  private String make;
  private String model;
  private int year;

  public Car(String make, String model, int year) {
    this.make = make;
    this.model = model;
    this.year = year;
  }

  public String getMake() {
    return make;
  }

  public String getModel() {
    return model;
  }

  public int getYear() {
    return year;
  }
}

class Main {
  public static void main(String[] args) {
    try {
      Class carClass = Class.forName("Car");
      System.out.println("The class of Car using Class.forName() is: " + carClass.toString());
    } catch (ClassNotFoundException e) {
      System.out.println("Class not found: " + e.getMessage());
    }
  }
}

Output :

The class of Car using Class.forName() is: class Car

Explanation : In this example, we use the Class.forName() method to get the Class object that represents the Car class. This method takes a string argument that is the fully qualified name of the class. We pass "Car" as the argument. Note that the Class.forName() method can throw a ClassNotFoundException, so we wrap it in a try-catch block. If the class is not found, we print an error message to the console.

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Java Program to Determine the class of an Object

What is class in Java ?

What is Object in Java ?

Sysntax :

Ways to Determine the class of Object :

Example : using instanceof operator

Output :

Example : using getClass() Method

Output :

Example : Using Class.forName() method

Output :

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