constructor with private access modifier

[Abhishek Reddy]

A private constructor means only code within the class itself can instantiate an object of that type, so if the private-constructor class wants to allow an instance of the class to be used, the class must provide a static method or variable that allows access to an instance created from within the class.

I didnot uderstand this point :If the private-constructor class wants to allow an instance of the class to be used, the class must provide a static method or variable that allows access to an instance created from within the class.

Please make me understand this point
Thanks in advance

[Jesper de Jong]

It's just a plain and clear English sentence, but your native language probably isn't English. I'll try to explain it with code.

public class MyClass {
    // Private constructor; this cannot be called outside the class
    private MyClass() { }
 
    // Public static method that calls the private constructor; this method
    // can be called from other classes to get an instance of MyClass
    public static MyClass newInstance() {
        return new MyClass();
    }
}

An example of where this technique is useful is in the implementation in Java of the singleton design pattern.
[ August 17, 2006: Message edited by: Jesper Young ]