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What is the difference between default constructor and parameterized constructor?
A default constructor is one that has no parameters (C++ also calls constructors with all default parameters a default constructor), while a parameterized constructor is one that has at least one parameter without a default value. Default constructors can be provided by the compiler if no other constructors are defined for that class or any class the class inherits from, while parameterized constructors must always be defined by the developer.
When a object is passed to a function as argument why it is not generating an error if the parameterized constructor is defined and not the default constructor?
default constructor is used only when the programmer does not use a constructor to initialize objects. Once the programmer defines a constructor then the default constructor is no longer used
What is mean constructor in java?
A parameterized constructor in java is just a constructor which take some kind of parameter (variable) when is invoked. For example. class MyClass { //this is a normal constructor public MyClass(){ //do something } //this is a parameterized constructor public MyClass(int var){ //do something } //this is another parameterized constructor public MyClass(String var, Integer var2){ //do something } }
How do you get a default constructor?
The default constructor is an empty (only call the super constructor) with no parameters constructor inserted by the java compiler when you don't define a constructor in your class. If you write something like this: public class NoConstructorClass{ //no constructor goes here } Then you get something like this: public class NoConstructorClass{ public NoConstructorClass(){ // Default constructor that you didn't write super(); } }
Default constructor in java?
If you don't type a constructor into your class code, a default constructor will be automatically generated by the compiler. The default constructor is ALWAYS a no-arg constructor. (Obviously the compiler has no clue what all arguments you might want for your class. So it takes the safe way out with a no argument constructor) A no-arg constructor is not necessarily the default (i.e., compiler-supplied) constructor, although the default constructor is always a no-arg constructor. The default constructor is the one the compiler provides! While the default constructor is always a no-arg constructor, you're free to put in your own no-arg constructor.
How is the default constructor equivalent to a constructor having default arguments?
Any constructor that can be invoked without explicitly passing any arguments is a default constructor. Note that there can be only one default constructor so there can only be one constructor where all arguments have default values or one constructor that has no arguments, but not both. A constructor where all arguments have default values is a useful means of combining two or more constructors into a single default constructor, thus reducing verbosity and code duplication.
What is another name of default constructor?
No-Arg Constructor
What is an empty constructor?
An empty constructor takes no arguments and calls the default constructor
What is the need of parameterized constructor?
Parametrized constructors are used to increase the flexibility of a class, allowing objects to be instantiated and initialised in more ways than is provided by the default and copy constructors alone. If you define any parametrized constructor, including a copy constructor, you will lose the default constructor generated by the compiler and must declare your own if you need one. The default constructor can also be parametrized, but each parameter must include a default value in the declaration, so that it can be called without any parameters.
Is Java always provides a default constructor to a class?
Correct. If you omit a constructor, Java will assume that an empty one exists. Given the following code for a class: class MyClass { } You can make a call to the default constructor: MyClass mc = new MyClass(); Just keep in mind that the default constructor "goes away" if you implement another constructor. class MyClass { public MyClass(String str){ } } This line will now result in a "cannot find symbol" compiler error: MyClass mc = new MyClass();
Why Java always provides a default constructor to class when you use another constructor default constructor remove?
Classes in Java inherit constructors from their parent classes. If you don't explicitly define a parent class, then Object is used, which has only the default empty constructor. That "default" constructor is only there when defined by the parent class, so classes which do not have a no-argument constructor will not allow subclasses to automatically use it. This is implemented this way because of the special nature of constructors. Java could not always provide a default constructor because it could not guarantee that all class members would be properly created or initialized.
What is first call in struts2 default constructor or validate method?
Default Constructor will be called first . If you override Validate method , then validate method will be called .
