How do you get a default constructor?

Answer 1

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();

}

}

Answer 2

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 .

Answer 3

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() {

...

}

}

Answer 4

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.

Answer 5

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.

Answer 6

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)

Determine Whether a Default Constructor Will Be Created

The following example shows a Lamborghini class with two constructors:

class Lamborghini {

Lamborghini() { }

Lamborghini(String name) { }

}

Will the compiler put in a default constructor for the class above? "No!" What about for the following variation of the class?

class Lamborghini {

Lamborghini(String name) { }

}

Now will the compiler insert a default constructor? "No Again!" What about this class?

class Lamborghini { }

Now we're talking. The compiler will generate a default constructor for the preceding class, because the class doesn't have any constructors defined. OK, what about this one below?

class Lamborghini {

void Lamborghini() { }

}

You might be tempted to say that, the compiler won't create one, since there already is a constructor in the Lamborghini class? Take another look at the Lamborghini class.

What's wrong with the Lamborghini() constructor? It isn't a constructor at all! It's simply a method that happens to have the same name as the class. Remember, the return type is a dead straight way to tell us that we're looking at a method, and not a constructor. So, here again the compiler will put the default no-arg constructor in the class.

Answer 7

Default constructors are useful in those situations where the object need not be initilaised before it is used. The instance variables may be set later on using get and set methods.

Answer 8

Default constructor in Java initialises all instance variables with default values.

class program {

int a; // default constructor initialises a to 0

}

Answer 9

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.