重载包含显式构造函数的类，并调用super（）

Question

It appears that if a programmer supplied constructor, with a call to super ( ) is used, no other constructor can be invoked in that class ( ie it can't be overloaded). Is this normal behavior that is inherent to Java? Why?

abstract class Four {
     Four (  ) { }
     Four (int x) { }
    }
class Three extends Four  {
    public Three ( String name) { }
    Three (int t, int y) { }
    }
class Two extends Three {
    Two ( ) { super ( "number");  } 
//  Two (int t, int y) { }  //causes an error when uncommented
    }
class One extends Two {
    public static void main (String [ ] args) {
        new One ( ); 
        }
    }

Answer 1

no other constructor can be invoked in that class ( ie it can't be overloaded).

That's not true at all. The problem with your Two(int t, int y) constructor is that it doesn't chain to any constructor explicitly, meaning that there's an implicit super() call - which fails as there are no parameterless constructors in Three ¹ . You can fix that in two ways:

• Chain directly to a super constructor

   Two (int t, int y) { super("number"); } 

• Chain to a constructor in the same class

   Two (int t, int y) { this(); } 

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¹ It doesn't have to be parameterless, strictly - if you add a Three(String... values) constructor, that's okay. You need to have a constructor that can be invoked with an empty argument list.