When exactly does class initialization occur during application startup?

Class initialization in Java occurs upon the first active use of the class, which can be:

• When creating the first instance of the class (via new).
• When calling a static method of the class.
• When accessing a static field of the class.
• When loading the class through reflection.

At the moment of initialization, the static initialization block is executed, and static fields are initialized.

Example:

public class Example {
    static {
        System.out.println("Class initialized");
    }

    public static void method() {
        System.out.println("Static method called");
    }
}

// Call
Example.method(); // This will trigger class initialization

Thus, class initialization occurs once upon the first active use of the class.