Is it possible to declare a constructor as private in a class?

In Java, a constructor can be declared with any access modifier, including private. A private constructor is used, for example, in the Singleton pattern to prevent creating instances of the class from outside.

Example of a private constructor:

public class Singleton {
    private static Singleton instance;

    private Singleton() {
        // private constructor
    }

    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
}

Thus, a private constructor restricts object creation of the class only within the class itself.