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What is Default constructor?

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Answered 2010-05-06 21:10:25

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




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You are free to override the default constructor whenever you like. In fact, if you want to keep the default constructor when you also need a parameterized constructor, you have to override the default constructor in order to use it. Once you've written the parameterized constructor, the default constructor goes away.

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

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.

if we write a code in java then we don't mansion a default constructor in it then compiler by default provide a default constructor and the main impotent role of default constructor in our program is that it initialize the member of the class then it is reason compiler provide a default constructor in our java program code .

Default constructor in Java initialises all instance variables with default values. class program { int a; // default constructor initialises a to 0 }

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.

Default constructors is a term having to do with computer programming. A default constructor refers to a constructor that is automatically generated when an explicit constructor is missing.

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

A default constructor is generated for a class if we did not specify any constructor for it. A default constructor is a public constructor that takes no arguments. For example: public class Test { } The compiler will turn this into: public class Test { public Test() { ... } }

There is no such thing as an access specifier in Java. There are access modifiers. The default for a default constructor is 'public'.

An empty constructor takes no arguments and calls the default constructor

A default constructor is a constructor that takes no arguments.Here's a sample:class c{int a,b;c() //Constructor 1{a=2;b=1;}c(int x, int y) //Constructor 2{a=x;b=y;}};Here, Constructor 1 is called the default constructor, while Constructor 2 is a parameterized constructor.

Default Constructor Parameterised Constructor Non Parameterised 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.

Any time you don't write any constructor for your class, the compiler supplies the default constructor. In other words, if you wrote a constructor the compiler won't.

That depends on how you define body of class. If you do not define constructors then compiler will provide default constructor and it is not overloaded. If you create your own constructor you automatically overload default constructor.

There is no such thing as 'the general syntax of a default constructor'. A default constructor is one that is generated by the compiler if you don't specify any constructors at all. Semantically speaking, it is public and takes no arguments, but this is not 'syntax'.

You get a default constructor when you do not provide a constructor that takes no arguments. Such a (compiler provided) default constructor will only set up the object (initialize vftables and vbtables) and call constructors for base classes, but it will take no further action, with the result that your object will not be in a properly initialized state.

No. If you do not write a constructor for you classes, the default Object constructor can still be used.

A parameter constructor is a constructor within a class with some arguments in it. class abc { abc()---------------------------------Default Constructor { } abc(int d)---------------------------Parameter Constructor { } }

To ensure that an object for the class can be created even though the programmer did not explicitly create one. However, if you create a constructor with arguments, the system will not create the default constructor for your class

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.

Default Constructor will be called first . If you override Validate method , then validate method will be called .

Yes, If you don't a default constructor will be created for you.

one:A class have only one default constructor.If a class doesn't contain any constructor at run time default constructor is provided by JVM. Mugdha

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