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How do explicitly invoke superclass constructor from a subclass?
Wiki User
∙ 13y ago
Using the super keyword.
If you call super() from within your constructor, it will explicitly invoke the superclass version of the constructor.
Wiki User
∙ 13y ago
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How do explicitly invoke overridden superclass method from a subclass?
Use the super keyword. Example: public class Super { public void methodToOverride() { } } public class Sub { @Override public void methodToOverride() { super.methodToOverride(); } }
How constructor called?
You cannot invoke a constructor explicitly. It will get invoked implicitly when you call the new keyword on the class to create an object of the class. Ex: private ClassExample obj = new ClassExample(); here this new keyword usage on the ClassExample class will invoke the constructor of this class and create an object of that class.
Can you call a constructor from another if a class has multiple constructors?
Yes. All you need to do is to specify the correct number of arguments to invoke the correct constructor.
How is a constructor in the super class called?
By using the reference super(); When you invoke super(); the JVM knows that you are trying to invoke the constructor from the parent class and calls the super class constructor automatically. In fact, the invocation to super(); is usually the first line of any class constructor. This is done to ensure that all the parent class objects are initialized before the current child class is created.
How do you call an abstract class from main method?
An abstract class cannot have a constructor and hence you cannot invoke the constructor of the class - i.e., you can instantiate an abstract class and hence you cannot call the constructor of an abstract class.
What is the uses of constructor in java?
The constructor will invoke all constructors in the inheritance hierarchy to ensure that all the parent classes of the current classes get initialized when the current class is instantiated.
What is the technical name for calling a base class constructor using derived class constructor?
You cannot actually call any constructor, you can only invoke construction, either by instantiating a static instance of a class or by dynamically creating one with the new operator. In the case of base class construction via a derived class, the base class constructor is invoked by the derived class' initialisation list. Every class constructor has an initialisation list whether you define one or not (the compiler will generate one automatically if you don't). When you derive one class from another, the derived class initialisation list invokes a call to the base class default constructor. The only exception is the compiler-generated copy constructor which automatically calls the base class copy constructor. If you define your own initialisation list, then you can explicitly invoke any base class constructor overload, thus making your construction code all the more efficient. However, copy constructors should always invoke the base class copy constructor, so if you define a copy constructor, you must explicitly invoke the base class copy constructor -- the compiler will not invoke it implicitly from a user-defined copy constructor. While many programmer's use the constructor's body to initialise a class, this is highly inefficient. Even if you don't specify an initialisation list, one is created for you, resulting in every base class and every member variable being initialised twice, which can quickly add up to a substantial cost in performance. The constructor's body should only really be used for initialisation when it would be difficult or impossible to do so from the initialisation list. Remember that your object doesn't physically exist until initialisation is complete, so you may not have access to some members, particularly base class members, at certain points in the initialisation process. Initialisation must be done from the ground up, starting with the base classes and ending with the actual class members, and all in the order they were declared. Note that only direct base classes (or virtual base classes) should be invoked from the initialisation list. The base classes themselves should invoke their own base class constructors, if they have any. Thus no matter which derivative you construct, the least-derived class is always constructed first.
What is the function of this in java?
this in java is a keyword that refers to the current object of the class. It is also used in constructor overloading when you want to invoke one constructor from another within the same class.
What is the method of constructor overloading in c plus plus?
Constructor overloading, just like any function's overloading, is where more than one configuration of parameters exists for the function. Based on the number and type of the parameters, different versions of the function can be resolved by the linker. This is typically used in the constructor as the default constructor (no parameters), the copy constructor (one reference parameter of the same type as the class), and the conversion constructor (any other combination of parameters).
How do we invoke a constructor?
In Java, objects are constructed. Every time you make a new object, at least one constructor is invoked. Every class has a constructor, although if you don't create one explicitly, the compiler will build one for you. Ex: class Test { public Test() { } // this is Test's constructor public void Test() { } // this is a badly named, // but legal, method } If you see the example above, you would have realized that the constructor looks a lot like methods. Below are the main distinguishing factors between the constructor and normal methods: 1. The Constructor's name is exactly the same as the name of the class 2. They do not have a return type (Please remember this. A Constructor cannot have a return type as part of the code) 3. Constructors cannot be static, abstract or final
What is dynamic constructor?
In Java classes we can declare multiple constructors. The JVM would dynamically decide which constructor to invoke based on the parameters passed from the calling class. Ex: public class Test { public Test(){ ... } public Test(String arg1){ ... } public Test(String arg1, int arg2){ ... } } In the above class, there are 3 different constructor declarations. Whenever a constructor is invoked from a calling class, the JVM would decide which one to invoke based on the number of arguments passed.
How do you invoke the constructor function in c plus plus?
There is no such thing as a constructor function in C++ (constructors have no return value, not even void, and cannot be called like regular functions). Constructors are invoked rather than called directly, either by declaring a static variable of the class type, or via the C++ new operator.
