constructor

[harish shankarnarayan]

U cannot invoke an instance(non-static method or access an instance variable )until after the super constructor has run???

can anyone explain watdoes the above line mean with a simple piece of code

[Edisandro Bessa]

Hi harish,

The affirmation is correct ! Any instance methods or properties cannot be accessed before its super constructor runs.

In order to your class exist, its super classes must exist before. It

[Edisandro Bessa]

Hi harish,

The affirmation is correct ! Any instance methods or properties cannot be accessed before its super constructor runs.

In order to your class exist, its super classes must exist before. It's a pre-requisite.

Please take a look at the following code :

class Car{
    
    // Common properties for all cars
    
    public String color;
    public String chassiID;
    
    public Car(){
        color = "None";
        chassiID="None";
    }
}
 
class Ferrari extends Car{
    
    // Ferrari specific properties
    
    public String ferrariSeries;
    
    public Ferrari(){
        ferraiSeries = "FerrariEnzo";
        
        // Will not compile here because Car must exist before
        super();
    }
}

So now, just changing the order for super() call the code will compile fine.

    // Ferrari constructor
    public Ferrari(){
        super();
 
        // Now the code will compile because Car class already exists.
        ferraiSeries = "FerrariEnzo";
    }

[harish shankarnarayan]

U cannot invoke an instance(non-static method or access an instance variable )until after the super constructor has run

this is saying somrthing abt accessing the instance var or method before running the super class.

i Didnt get ur point
it says we can access static methods but

[Edisandro Bessa]

this is saying somrthing abt accessing the instance var or method before running the super class.

Yes, your instance methods or variables will be accessible only after super constructor has ran.

it says we can access static methods but

Concerning static methods and static variables, it's not related to new keyword.

When you access a static member in your class, the class is already expected to be loaded by JVM. Don't confuse with constructor which is called when you creates a new class instance via new keyword.

Anyway, the rules for access instance or static members within a constructor is the same. [B] You cannot use ANY member after super's constructor has run.

If you still are confused please let me know.