How Does Java Handle Class and Interface Initialization Order?

Java Order of Initialization and Instantiation Clarification

Class Initialization

The initialization of a class involves setting values for compile-time constant fields, initializing the superclass (if uninitialized), and executing static initializers. However, initializing a class does not automatically initialize its implemented interfaces.

Initialization of Interfaces

Interfaces are initialized independently when accessed for the first time, especially when reading non-compile-time constant fields. This access can trigger recursive initialization if the field is used in initializer blocks. Interfaces are initialized before or after superclasses, depending on which method is accessed first.

Role of Super() Constructor Call

An explicit call to the superclass constructor in a constructor invocation changes which constructor is invoked, but it does not affect the overall initialization ordering.

Clarifications and Missing Details

• Interfaces are processed recursively, but not in a separate stack.
• Superclass initialization always occurs before the current class's non-compile-time constant fields are initialized.
• Instance variable initialization occurs prepended to the current constructor as it returns, and follows the textual order from top to bottom.
• Accessing static fields with compile-time constant values does not trigger initialization.

The above is the detailed content of How Does Java Handle Class and Interface Initialization Order?. For more information, please follow other related articles on the PHP Chinese website!