needed clarificarions on constructors

[kashyapkeshav]

Hi am learning JAVA . in the below example

1.how exactly the two samples differs please clarify

Class A {
int i=10;
}

and
Class A {
int i=10;
A(intj);//Initializing the constructor
}

2. Whats the necessity of initializing the constructor when u are defining the variable .

[wsaryada]

1. You second example is not correct, you might want something like this:

class A {
    int i = 10;

    A(int j) {
        // ...
    }
}

When you creating a class and doesn't provide a constructor it will have a default constructor. A constructor that doesn't have any parameter. A constructor is used to create an instance of corresponding class. The difference between your first and second example that your second example will not have the default constructor because you provided a constructor that take a single parameter. To instantiate your first class you can do it like A a = new A(); but the second A class can only be instantiate by A a = new A(0); You can't instantiate it using the default constructor.

2. You use constructor to instantiate or initialize objects or variables in your class. This is to make sure that it is in the state that you want when you class it running it function.

[kashyapkeshav]

Thank you saryada ,

i got a clear picture of it .

thank you very much