Question

I want to create custom class loader. But I am confused with loadClass(), does this method loads the specified class into memory?

If yes then why does the static block of the specified class is not invoked?

//main class

package custom_class_loader1;


public class Custom_class_loader1 {


    public static void main(String[] args) {

        try{
        CustomClassLoader c=new CustomClassLoader();
       Class c1= c.loadClass("custom_class_loader1.ABC");/**does this load ABC class into memory?**/

        }catch(Exception e)
        {
            System.out.println(e);

    }
}
}

Answer 1

When you load a class it doesn’t initalise it until it is used by default.

Invoking this method is equivalent to invoking loadClass(name, false);

Here false means don’t resolve the class.

One way to control this is to use the Class.forName()

public class Main {
    public static void main(String[] args) throws ClassNotFoundException {
        ClassLoader cl = new URLClassLoader(new URL[0], ClassLoader.getSystemClassLoader());
        System.out.println("unresolved Test");
        cl.loadClass("Test");
        // or
        Class.forName("Test", false, cl);

        System.out.println("\ninitialise Test");
        Class.forName("Test", true, cl);
    }
}

class Test {
    static {
        System.out.println("Loaded Test class");
    }
}

prints

unresolved Test

initialise Test
Loaded Test class