Using Static variables to Count Instances in Java

Last update on December 21 2024 10:02:06 (UTC/GMT +8 hours)

Static Variables:
Write a Java program to create a class called "Counter" with a static variable count. Implement a constructor that increments count every time an object is created. Print the value of count after creating several objects.

Sample Solution:

Java Code:

Counter.java

// Define the Counter class
public class Counter {
    // Static variable to keep track of the count of instances
    private static int count = 0;

    // Constructor increments the static variable count
    public Counter() {
        count++;
    }

    // Static method to get the value of count
    public static int getCount() {
        return count;
    }

    // Main method to test the Counter class
    public static void main(String[] args) {
        // Create several Counter objects
        Counter c1 = new Counter();
        Counter c2 = new Counter();
        Counter c3 = new Counter();

        // Print the value of count
        System.out.println("Count: " + Counter.getCount());
    }
}

Output:

Count: 3

Explanation:

• Define the Counter class:
• The Counter class is defined using the class keyword.
• Static variable to keep track of the count of instances:
• A private static variable count is declared to keep track of the number of instances created.
• Constructor increments the static variable count:
• The constructor Counter() is defined to increment the count variable every time a new instance is created.
• Static method to get the value of count:
• A static method getCount() is defined to return the value of the static variable count.
• Main method to test the Counter class:
• The main method is defined to test the Counter class.
• Several Counter objects (c1, c2, c3) are created.
• The value of count is printed using the getCount() method.

Note on Java Static Members:

In the above exercise, the static members work by:

• Static Variable: The static variable count is shared among all instances of the Counter class. This means that every time a new Counter object is created, the same count variable is incremented.
• Constructor: The constructor is used to increment the static variable count whenever a new instance of the Counter class is created.

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