I have two classes :
First, with one constructor :
public class First {
First (ObjectA myObjectA) {
//do stuff
}
}
And Second, with two constructors :
public class Second {
Second (ObjectB myObjectB) {
//do something...
}
Second (ObjectC myObjectC) {
//do something else...
}
}
When I want to instantiate my First
class, Eclipse generates me an error ("The constructor is not visible"), I have to add public
to the constructor of First
:
First first = new First(myObject); //Error : "The constructor is not visble"
But when I instantiate my Second
class, I have no error :
Second second = new Second(myObjectC); //No error...
Notes: I instantiate First
in an other class, but I instantiate Second
in First
. First
and Second
are in the same package.
Can you explain me why ?
A private constructor in Java is used in restricting object creation. It is a special instance constructor used in static member-only classes. If a constructor is declared as private, then its objects are only accessible from within the declared class. You cannot access its objects from outside the constructor class.
However, it's important to know what happens under the hood when no constructors are explicitly defined. The compiler automatically provides a public no-argument constructor for any class without constructors. This is called the default constructor.
If we declare a constructor as private we are not able to create an object of a class. We can use this private constructor in the Singleton Design Pattern.
No access modifier for your constructor makes it package private. Assuming that First and Second are in the same package, you can call Second's constructors from first. Another class from another package, however, cannot access any of the constructors.
Your class must be in 2 packages. If you don't mention any explicit access modifier Java will consider them as default access modifier. Then you can only access them through the same package only.
Access Modifiers (From least access to highest access)
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