Contains an access modifier followed by the name of the class and some parameters. More specifically:
public class MyClass {
//Constructor
public MyClass() {
}
}
1. You need not code them explicitly. Java will automatically place a default constructor
2. You can pass arguments to the constructor
3. They can return only an object of type of that class
4. They can be made private
5. They would be executed always (Everytime a class is instantiated)
I assume you mean the constructor in a programming language. A constructor is a program that runs automatically every time an object is created. Details vary, depending on the language. In Java for example, the constructor has the same name as the class. In some other languages, the constructor has a specific reserved name.
Two key points to remember about constructors are that they have no return type and their names must exactly match the class name
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.
An empty constructor takes no arguments and calls the default constructor
An implicit constructor call will always call the default constructor, whereas explicit constructor calls allow to chose the best constructor and passing of arguments into the 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
Java has 2 types of constructors based on parameters passed:Default or parameter-less constructor: A constructor which does not accept any arguments.Parametrized constructor: A constructor which accepts one or more arguments.Similarly based on Access modifier also we have:Public constructor - Class can be instantiated by anyonePrivate constructor - Class cannot be instantiated by anyoneProtected constructor - Class can be instantiated only by sub classes
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.
An empty constructor takes no arguments and calls the default constructor
An implicit constructor call will always call the default constructor, whereas explicit constructor calls allow to chose the best constructor and passing of arguments into the 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
yes we can call constructor
Constructor is used to do something (written in constructor) immediately after object creation.
There is no such thing as a default parameterized constructor. The default constructor is always the 'no-arg' constructor and does not take any parameters or arguments as input
When any constructor is deffined in your class, the java compiler create a default no argument constructor for you. This constructor only have an invocation to the super class constructor (" super( ) ").
Java has 2 types of constructors based on parameters passed:Default or parameter-less constructor: A constructor which does not accept any arguments.Parametrized constructor: A constructor which accepts one or more arguments.Similarly based on Access modifier also we have:Public constructor - Class can be instantiated by anyonePrivate constructor - Class cannot be instantiated by anyoneProtected constructor - Class can be instantiated only by sub classes
All Java programs would have a constructor... public class Test { public Test(){ ... } ..... } This is a constructor. Even if you dont code the constructor Java would automatically place a default constructor for compilation.
No-Arg Constructor
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.