Java new Keyword

The new keyword in Java is used to create new objects. When you use new, it allocates memory for a new object and returns a reference to that memory.

Table of Contents

1. Introduction
2. new Keyword Syntax
3. Understanding new
4. Examples
   • Creating a New Object
   • Using new with Arrays
   • Using new with Classes
5. Real-World Use Case
6. Conclusion

Introduction

The new keyword is essential in Java for creating new instances of classes (objects) and arrays. It dynamically allocates memory for the new object and returns a reference to that object.

new Keyword Syntax

The syntax for using the new keyword is as follows:

ClassName objectName = new ClassName();

Example:

Car myCar = new Car();

Understanding new

When you create an object using new, it performs the following steps:

1. Allocates memory for the new object.
2. Calls the constructor of the class to initialize the object.
3. Returns a reference to the newly created object.

Examples

Creating a New Object

Let’s create a new object of the Car class.

Example

class Car {
    String color;
    String model;

    void drive() {
        System.out.println("The car is driving.");
    }
}

public class Main {
    public static void main(String[] args) {
        Car myCar = new Car(); // Creating a new Car object
        myCar.color = "Red";
        myCar.model = "Toyota";
        System.out.println("Car model: " + myCar.model);
        myCar.drive();
    }
}

Output:

Car model: Toyota
The car is driving.

Using new with Arrays

You can also use new to create arrays.

Example

public class Main {
    public static void main(String[] args) {
        int[] numbers = new int[5]; // Creating a new array of integers
        numbers[0] = 10;
        numbers[1] = 20;
        numbers[2] = 30;
        numbers[3] = 40;
        numbers[4] = 50;

        for (int i = 0; i < numbers.length; i++) {
            System.out.println("Element at index " + i + ": " + numbers[i]);
        }
    }
}

Output:

Element at index 0: 10
Element at index 1: 20
Element at index 2: 30
Element at index 3: 40
Element at index 4: 50

Using new with Classes

You can use new to create instances of any class.

Example

class Person {
    String name;
    int age;

    // Constructor
    Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    void display() {
        System.out.println("Name: " + name + ", Age: " + age);
    }
}

public class Main {
    public static void main(String[] args) {
        Person person = new Person("Alice", 30); // Creating a new Person object
        person.display();
    }
}

Output:

Name: Alice, Age: 30

Real-World Use Case

Creating a Bank Account Class

In real-world applications, you might use the new keyword to create instances of classes that represent real-world entities, such as bank accounts.

Example

class BankAccount {
    String accountNumber;
    double balance;

    // Constructor
    BankAccount(String accountNumber, double initialBalance) {
        this.accountNumber = accountNumber;
        this.balance = initialBalance;
    }

    void deposit(double amount) {
        balance += amount;
        System.out.println("Deposited: " + amount);
    }

    void displayBalance() {
        System.out.println("Account Number: " + accountNumber + ", Balance: " + balance);
    }
}

public class Main {
    public static void main(String[] args) {
        BankAccount account = new BankAccount("123456789", 500.0); // Creating a new BankAccount object
        account.deposit(150.0);
        account.displayBalance();
    }
}

Output:

Deposited: 150.0
Account Number: 123456789, Balance: 650.0

Conclusion

The new keyword in Java is used to create new objects and arrays dynamically. It is a fundamental part of object-oriented programming in Java, enabling the creation and initialization of instances of classes. Understanding how to use the new keyword is essential for working with objects and arrays in Java.