Using Static variables to Count Instances in Java
Java Static Members: Exercise-1 with Solution
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.
Java Code Editor:
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