Class.forname method

Class.forName("X") helps us to load class dynamically(at runtime) using its fully qualified name (package.classname) and JVM executes all its static block after class loading.

Note: It does not return the instance of Class.

forName() uses the classloader to invoke the class.

If a class already loaded in JVM, Class.forName()  does not load that class i.e. JVM keeps track of all the classes that have been previously loaded.

public class ClassForName {

       public ClassForName() {

              System.out.println("ClassForName Constructor");

       }

      

       public static String methodName = "ClassForName";

       static {

              System.out.println("static block in ClassForName");

       }
}

public class TestForname {

       public static void main(String[] args) {

              try {

                     Class c   = Class.forName("core.forname.ClassForName");

                     ClassForName name = (ClassForName)c.newInstance();

                    

                     System.out.println("The second time calls forName:");

                  Class c1 = Class.forName("core.forname.ClassForName");

                    

              } catch (InstantiationException | IllegalAccessException e) {

                     e.printStackTrace();

              } catch (ClassNotFoundException e) {

                     System.out.println("ClassNotFoundException");

              }

       }

}

Output:

The output is

static block in ClassForName

ClassForName Constructor

The second time calls forName:

JDBC Driver Is a Good Example

We generally uses it load the JDBC Drivers.

If class successfully loaded, the static initializer is called.

Class.forName("org.gjt.mm.mysql.Driver");
Connection con = DriverManager.getConnection(url, "myLogin", "myPassword");