Initialization of Classes ?

From "Thinking in Java":

Quote:

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It’s interesting to note that creating a reference to a Class object using ".class" doesn’t automatically initialize the Class object.

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When I try this:

Code:

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package myPackage1;

class Toy
{
        Toy(){};
}


public class ToyTest
{
        static void printInfo(Class cc)
        {
                System.out.println("Class name: " + cc.getName()
                                + " is interface? " + cc.isInterface());
        }

        public static void main(String[] args)
                        throws ClassNotFoundException, InstantiationException, IllegalAccessException
        {
                Class k = Toy.class;
                printInfo(k);
        }
}

---

I get the output:

Class name: myPackage1.Toy is interface? false

But isn't this class supposed to be not initiated ?

I will answer my own question:

Code:

---

class Toy
{
        Toy()
        {
                System.out.println("Initialized!");
        }
       
        static
        {
                System.out.println("Hello!");
        }
}

---

Code:

---

                Class k = Toy.class;
                printInfo(k);
               
               
                Class m = Class.forName("myPackage1.Toy");

---

My only comment is:

The constructor is not called, when the class is initialized. The output is:
Class name: myPackage1.Toy is interface? false
Hello!


So it seems a constructor is called not when the class is initialized, but when an instance of that class is created.

Initializing a class only calls the statements in the static{} block.

I would expect the Class object to be initialized when getName() is called.

Note that loading the class and initializing it are two separate steps.

The purpose of a constructor is to create an instance of the class, so it's no surprise that it doesn't run when the class is loaded or initialized.

More here: Execution

db

What if I have an instance variable in my class like int age and in my static block if I have something like this.age = 4;

Then what happens ?

Answering my own question:
You can't use "this" in a static block.