Can the class with private constructor be extended?

No, in case of outer classes.

The below program will generate compile time error.

 package org.javatutorials.accessModifer.protectedPackage;

class ClassWithPrivateConstructor {
    private ClassWithPrivateConstructor() {
        System.out.println("Hello from ClassWithPrivateConstructor");
    }

}

public class ExtendingClass extends ClassWithPrivateConstructor {

    public ExtendingClass() {
        System.out.println("Hello from ExtendingClass");
    }

    public static void main(String args[]) {

        new ExtendingClass();
    }
}

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