How to Create Array of Objects in Java?
In Java, an array of objects is used to store multiple instances of a class within a single array. This allows us to easily manage a collection of objects when working with large datasets or collections.
Example:
In the below example, we will demonstrate how to create an array of Student objects and initialize them with different values. Then, we will display the details of each student object stored in the array.
class Student {
int id;
String n;
// Constructor to initialize student object
Student(int id, String n) {
this.id = id;
this.n = n;
}
// Method to display student details
void display() {
System.out.println("ID: " + id + ", Name: " + n);
}
}
public class Main {
public static void main(String[] args) {
// Creating and initializing an
// array of Student objects
Student[] s = {
new Student(1, "Ram"),
new Student(2, "Shyam")
};
// Displaying student details
for (Student s1 : s) {
s1.display();
}
}
}
Output
ID: 1, Name: Ram ID: 2, Name: Shyam
Explanation: The for loop iterates over each Student object in the “s" array. Inside the loop, s1.display() is called to print the details of each Student object.
Table of Content
Creating an Array Of Objects In Java
In Java, we can create an array of objects just like any other array. The only difference is that the array elements are references to objects rather than primitive types.
1. Declaration: To declare an array of objects, specify the class name followed by square brackets [].
Class_Name[ ] objectArrayReference;
Student[] students;
Alternatively, we can also declare an Array of Objects as,
Class_Name objectArrayReference[ ];
Student students[];
2. Instantiation: After declaring the array, instantiate it using the new keyword, specifying the size of the array.
Class_Name obj[ ]= new Class_Name[Array_Length];
students = new Student[3]; // An array of 3 Student objects
3. Initialization: Each element of the array must be initialized individually, either via constructor or setter methods.
Structure of an Array Objects
The below figure shows the structure of an Array of Objects (here object is “bike”).
Initializing Array Of Objects
After creating an array of objects, the elements need to be initialized. There are two common ways to do this:
1. Using the constructor
At the time of creating actual objects, we can assign initial values to each of the objects by passing values to the constructor separately. Individual actual objects are created with their distinct values.
Example:
// Java program to demonstrate initializing
// an array of objects using constructor
class GFG {
public static void main(String args[]) {
// Declaring an array of student
Student[] arr;
// Allocating memory for 2 objects
// of type student
arr = new Student[2];
// Initializing the first element
// of the array
arr[0] = new Student(1, "Sai");
// Initializing the second element
// of the array
arr[1] = new Student(2, "Omm");
// Displaying the student data
System.out.println(
"Student data in student arr 0: ");
arr[0].display();
System.out.println(
"Student data in student arr 1: ");
arr[1].display();
}
}
// Creating a student class with
// id and name as a attributes
class Student {
public int id;
public String n;
// Student class constructor
Student(int id, String n)
{
this.id = id;
this.n = n;
}
// display() method to display
// the student data
public void display()
{
System.out.println("Student id is: " + id + " "
+ "and Student name is: "
+ n);
System.out.println();
}
}
Output
Student data in student arr 0: Student id is: 1 and Student name is: Sai Student data in student arr 1: Student id is: 2 and Student name is: Omm
2. Using Setter Methods
We can create objects first and then assign values using setter methods. A member function of the respective class is created and that is used to assign the initial values to the objects.
Example:
// Java program to demonstrate initializing
// an array of objects using a method
class GFG {
public static void main(String args[]) {
// Declaring an array of student
Student[] arr;
// Allocating memory for 2 objects
// of type student
arr = new Student[2];
// Creating actual student objects
arr[0] = new Student();
arr[1] = new Student();
// Assigning data to student objects
arr[0].setData(1, "Sai");
arr[1].setData(2, "Omm");
// Displaying the student data
System.out.println(
"Student data in student arr 0: ");
arr[0].display();
System.out.println(
"Student data in student arr 1: ");
arr[1].display();
}
}
// Creating a Student class with
// id and name as a attributes
class Student {
public int id;
public String n;
// Method to set the data to
// student objects
public void setData(int id, String n)
{
this.id = id;
this.n = n;
}
// display() method to display
// the student data
public void display()
{
System.out.println("Student id is: " + id + " "
+ "and Student name is: "
+ n);
System.out.println();
}
}
Output
Student data in student arr 0: Student id is: 1 and Student name is: Sai Student data in student arr 1: Student id is: 2 and Student name is: Omm
