Active Oldest Votes. Don't know where you read that, but it's wrong. The assignment does. Your claim doesn't. Improve this answer. Lightness Races in Orbit Lightness Races in Orbit k 70 70 gold badges silver badges bronze badges. I've seen answers downvoted when the premise of the question is flawed. That was my guess. Downvote not mine, but I'd guess that it's because the question isn't really answerable.
Doesn't reflect on the answer, but what can you do? I didn't downvote, I'm not sure where I read about the 2 constructor thing, but I'm looking at it now and it makes sense. Thanks — Henry V. MadPhysicist There is a certain irony about downvoting an answer because the question is unanswerable There certainly is. Although I've seen it happen enough times in practice to be desensitized. Not implying that it applies here. An SQL time string? Seems pretty random.
Why SQL? Anyway, if you want to provide a deserialiser, I would prefer this to be a free factory function. A timestamp — newbie. Your way is very tightly coupled - each module needs to know about each other module.
You cannot possibly produce a well-maintainable and well-tested Enterprise product like this. I recommend a book on scalable software design! Show 10 more comments. A Java constructor parameter can have the same name as a field.
If a constructor parameter has the same name as a field, the Java compiler has problems knowing which you refer to. By default, if a parameter or local variable has the same name as a field in the same class, the parameter or local variable "shadows" for the field. Look at this constructor example:. Inside the constructor of the Employee class the firstName , lastName and birthYear identifiers now refer to the constructor parameters, not to the Employee fields with the same names.
Thus, the constructor now just sets the parameters equal to themselves. The Employee fields are never initialized. To signal to the Java compiler that you mean the fields of the Employee class and not the parameters, put the this keyword and a dot in front of the field name.
Here is how the Java constructor declaration from before looks with that change:. You call a constructor when you create a new instance of the class containing the constructor. Here is a Java constructor call example:. This example invokes calls the no-argument constructor for MyClass as defined earlier in this text.
In case you want to pass parameters to the constructor, you include the parameters between the parentheses after the class name, like this:. This example passes one parameter to the MyClass constructor that takes an int as parameter. In Java it is possible to call a constructor from inside another constructor. When you call a constructor from inside another constructor, you use the this keyword to refer to the constructor. Here is an example of calling one constructor from within another constructor in Java:.
Notice the second constructor definition. Inside the body of the constructor you find this Java statement:. The this keyword followed by parentheses and parameters means that another constructor in the same Java class is being called. Which other constructor that is being called depends on what parameters you pass to the constructor call inside the parentheses after the this keyword.
In this example it is the first constructor in the class that is being called. In Java a class can extend another class. When a class extends another class it is also said to "inherit" from the class it extends. The class that extends is called the subclass, and the class being extended is called the superclass. Inheritance is covered in more detail in my tutorial about inheritance in Java. A class that extends another class does not inherit its constructors.
However, the subclass must call a constructor in the superclass inside of its the subclass constructors! If a subclass calls another constructor within itself, then the called constructor must call the superclass constructor. Look at the following two Java classes. The class Car extends inherits from the class Vehicle. Notice the constructor in the Car class.
It calls the constructor in the superclass using this Java statement:. Using the keyword super refers to the superclass of the class using the super keyword. When super keyword is followed by parentheses like it is here, it refers to a constructor in the superclass. In this case it refers to the constructor in the Vehicle class. Because Car extends Vehicle, the Car constructors must all call a constructor in the Vehicle.
The access modifier of a constructor determines what classes in your application that are allowed to call that constructor. The access modifiers are explained in more detail in the text on Java access modifiers. For instance, if a constructor is declared protected then only classes in the same package, or subclasses of that class can call that constructor. A class can have multiple constructors, and each constructor can have its own access modifier. Note that we now have two constructors : a default constructor that will be called in the default case, and a second constructor that takes two parameters.
You can have constructors in a class According to Oracle docs. You can create many constructors but with different signatures. This concept is known as Constructor Overloading and is quite similar to function overloading. A constructor is called depending upon the number and type of arguments passed. The other constructors must have different parameters. Additionally constructors which contain parameters which are given default values, must adhere to the restriction that not all parameters are given a default value.
It is used for following purposes. What is destructor in OOP? In object-oriented programming, a destructor sometimes abbreviated dtor is a method which is automatically invoked when the object is destroyed. In such languages, unlinking an object from existing resources must be done by an explicit call of an appropriate function usually called Dispose. The compiler will implicitly declare default constructor if not provided by programmer, will define it when in need.
Compiler defined default constructor is required to do certain initialization of class internals. It is declared using the virtual keyword. But, when base class pointer contains the address of the derived class object, always executes the base class function.
An abstract class is a class that is designed to be specifically used as a base class. An abstract class contains at least one pure virtual function.
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