List<Dog> is a subtype of List<? extends Animal>, but not a subtype of List<Animal>. Why is List<Dog> not a subtype of List<Animal>? Consider the following example: void mySub(List<Animal> myList) { myList.add(new Cat()); } If you were allowed to pass a List<Dog> to this function, you would get a run-time error. EDIT: Now, if we use … Read more
As of TS3.4 there is no partial type parameter inference. Either you let the compiler try to infer all the type parameters, or you specify all the type parameters. (Well, there are default type parameters but that doesn’t give you what you want: you want to infer the type parameters you leave out, not assign … Read more
What exactly are you trying to achieve? Having two different activities with a common ui, except for some variables or parts of the layout? In this case, I suggest having a base abstract activity, and two concrete inherited subclasses. You define all the common behaviour in the base activity, and have abstract methods for the … Read more
You want to ‘inherit’ from Person’s prototype object: var Person = function (name) { this.name = name; this.type=”human”; }; Person.prototype.info = function () { console.log(“Name:”, this.name, “Type:”, this.type); }; var Robot = function (name) { Person.apply(this, arguments); this.type=”robot”; }; Robot.prototype = Person.prototype; // Set prototype to Person’s Robot.prototype.constructor = Robot; // Set constructor back to … Read more
extends is for extending a class. implements is for implementing an interface The difference between an interface and a regular class is that in an interface you can not implement any of the declared methods. Only the class that “implements” the interface can implement the methods. The C++ equivalent of an interface would be an … Read more
If you really want to fake multiple inheritance in PHP 5.3, you can use the magic function __call(). This is ugly though it works from class A user’s point of view : class B { public function method_from_b($s) { echo $s; } } class C { public function method_from_c($s) { echo $s; } } class … Read more