why this output in java program print value 300

sinsen526 :

I have following java program,

class A{
    int a=100;

    A(int i){

    }
    {
        a=300;
    }
    void printA(){
        System.out.println("a : "+a);
    }

}
class Demo{
    public static void main(String args[]){
        A a1=new A(200);
        a1.printA();  //300
    }
}

but I cant understand why main method 'a1.printA(); ' as 300 can you explain some thing?

Stultuske :

class A{
    A(int i){

    }
    int a=100;
    {
        a=300;
    }
    void printA(){
        System.out.println("a : "+a);
    }

}
class Demo{
    public static void main(String args[]){
        A a1=new A(200);
        a1.printA();  //300
    }
}

OK, you set the value for that instance variable two times:

int a = 100;

this is the first one to execute. So, this is where it starts.

Then, you initialize your class, so your initialize block will be executed, which contains:

a=300;

this will overwrite the previous value.

You also pass a param to your constructor, but you don't use it. So this doesn't change the value of a.