statically loading

when we need to use the class definition, like new operator, invoking static method, accessing static variables etc, the JVM will load the class statically.

But just declare variable of that type, class loading actually don’t happen.

class StaticallyLoading {
    public static void main(String[] args) {
        C c = null;
        System.out.println("run here");
    }
}

After you compile this class successfully with class C definition, you run it as deleting the class C dependency at runtime.

This program can run normally.

But if you do some operations, like

• C c = new C();
• C.foo() Once the C class doesn’t exist at runtime, a NoClassDefFoundException will be thrown.

dynamically loading

• Class.forName(..)
• ClassLoader.findSystemClass(..)
• ClassLoader.findClass(..) ClassNoFoundException will be thrown if the class cannot be found at runtime.