Difference static behaviour between MyClass.class and Class.forName(“MyClass”)

Question

I'm not sure what's the difference of loading static variables/blocks between MyClass.class and Class.forName("MyClass"), for example, I have below class:

package test;
public class SampleClass{
    public static SampleClass instance = new SampleClass();
    private SampleClass(){
       System.out.println("SampleClass Instance Created");
    }
}

Then, in another class, I accessed the class object of above SampleClass by using:

System.out.println(SampleClass.class);

Then, the output will be:

class test.SampleClass

If I changed to use class.forName(), as below:

 System.out.println(Class.forName("test.SampleClass"));

Then, the output will be:

 SampleClass Instance Created
 class test.SampleClass

Does anybody can give me an explanation? Thanks a lot.

Answer 1

The call to the Class.forName("MyClass") causes the class to be loaded at runtime. JVM also initializes that class after the class has been loaded by the classloader, so static blocks get executed.

In your case you have a static field which is the instance of your class, as this static block get executed your object is being initialized. That's why you are seeing the System.out get printed.

The .class syntax is used to get the Class of the called class. It doesn't not load the class actually.

Reference:

• What does Class.forname method do?
• Java Doc
• Retrieving Class Object

Answer 2

Class.forName() uses the ClassLoader and tries to resolve class name at runtime, while .class is resolved at compile time.