Can we instantiate an abstract class directly? [duplicate]
I have read we can only instantiate an abstract class by inheriting it, but we cannot instantiate it directly.
However, I saw we can create an object with the type of an abstract class by calling a method of another class.
For example - LocationProvider
is an abstract class, and we can instantiate it by calling getProvider()
function in the LocationManager
class:
LocationManager lm = getSystemService(Context.LOCATION_PROVIDER);
LocationProvider lp = lm.getProvider("gps");
How is the abstract class instantiate here?
You can't directly instantiate an abstract class, but you can create an anonymous class when there is no concrete class:
public class AbstractTest {
public static void main(final String... args) {
final Printer p = new Printer() {
void printSomethingOther() {
System.out.println("other");
}
@Override
public void print() {
super.print();
System.out.println("world");
printSomethingOther(); // works fine
}
};
p.print();
//p.printSomethingOther(); // does not work
}
}
abstract class Printer {
public void print() {
System.out.println("hello");
}
}
This works with interfaces, too.
No, you can never instantiate an abstract class. That's the purpose of an abstract class. The getProvider
method you are referring to returns a specific implementation of the abstract class. This is the abstract factory pattern.
No, abstract class can never be instantiated.