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An abstract class can only be used as a base class which is extended by some other class, right? The constructor(s) of an abstract class can have the usual access modifiers (public, protected, and private (for internal use)). Which of protected and public is the correct access modifier to use, since the abstract type seems to indicate that technically a public constructor will act very much protected? Should I just use protected on all my constructors?
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An Abstract class can have access modifiers like private, protected, and internal with class members. But abstract members cannot have a private access modifier. An Abstract class can have instance variables (like constants and fields). An abstract class can have constructors and destructors.
Like methods, constructors can have any of the access modifiers: public, protected, private, or none (often called package or friendly). Unlike methods, constructors can take only access modifiers. Therefore, constructors cannot be abstract , final , native , static , or synchronized .
An abstract class can be inherited by any number of sub-classes, thus functionality of constructor present in abstract class can be used by them. The constructor inside the abstract class can only be called during constructor chaining i.e. when we create an instance of sub-classes.
since the abstract type seems to indicate that technically a public constructor will act very much protected
This is not correct. An abstract class cannot be directly instatiated by calling its constructor, however, any concrete implementation will inherit the abstract class' methods and visibility
So the abstract class can certainly have public constructors.
Actually, the abstract class's constructor can only be called from the implementation's constructor, so there is no difference between it being public or protected. E.g.:
public class Scratch { public static abstract class A { public A( int i ) {} } public static class B extends A { private B() { super(0); }; } } If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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