Can we count number of object created for a class?

Yes, we can count the number of objects created of a class in java. To understand this please sees the example below.

 Example:-

package demo;

public class TestDemo {
   static int count=0;
    TestDemo()
    {
        count=++count;
    }
   
  public static void main(String args[])
  {
     
      TestDemo obj1 = new TestDemo();
      TestDemo obj2 = new TestDemo();
      TestDemo obj3 = new TestDemo();
      TestDemo obj4 = new TestDemo();
 
        System.out.println(“You have created  ”+count+” times the object for TestDemo class.”);
}
}

Output of the above program is: [You have created 4 times the object for TestDemo class.]

As we all know that the execution of java program starts from the main method of the public class and whenever an object of the class is created, its constructor will be called automatically.

In the above example we created a class TestDemo and defined the TestDemo() constructer having logic for incrementing the integer type count variable by value one(1) also for the class. After this when we created the object of the TestDemo class in the main method with the blank constructor, the TestDemo() constructor called automatically and incremented the count variable by 1. Similarly, we created the object of the class TestDemo four times in the above example and TestDemo() constructor was also called for four times automatically and hence it incremented the integer type count variable’s (declared and defined in the TestDemo class)  value by 4 that’s why the result was showing 4.

So every time a new object for the class TestDemo will be created, the TestDemo() constructor will be run once for the every object creation and will increment the count variable value by one. So the count variable value will always be equal to the number of object created for the class TestDemo and we can check this by printing the value of count variable at the end of the program.