Why static initializers java

This is the main advantage of the Static Initialization Block in Java. Java does not care if this block is written after the main method or before the main method, it will be executed before the main method regardless. In the entire program, the Static Initialization Block will execute only one time. There can be many Static Initialization Blocks in a specific class. If we have many Static Initialization Blocks in Java then they are called in a manner in the order they are written in the program.

This block will not return anything. Checked exceptions cannot be thrown. We cannot use the "this" keyword since it does not have any instance. More info here docs. I am not surprised you can use reflection to discover things about a class without it resolving. Tell me more No return statements are supported. No arguments are supported.

No this or super are supported. Hmm where can I use it? Don't just bark! Inside Static Initializer. Inside Main Method. Hope this helps! Madan Sapkota Madan Sapkota Thanks Madan! Can static block be used instead of afterPropertiesSet of InitializingBean?

Yes, you can! Static initializer become called when the class gets loaded by the jvm. So its the really first phase where code gets executed. If you have a constructor too, the order would be: static initializer, constructor, afterPropertiesSet — Martin Baumgartner. The static block is a "static initializer". Alnitak Alnitak k 69 69 gold badges silver badges bronze badges.

Nope, no explicit way to invoke it, the class initializer is never represented by a Method instance but only invoked by the Java virtual machine. Execution Order Look at the following class, do you know which one gets executed first? How do Java instance initializer work? When are instance initializers useful? Thanks to Derhein. Community Bot 1 1 1 silver badge. Alexei Fando Alexei Fando 5 5 silver badges 12 12 bronze badges.

Vincent Ramdhanie Vincent Ramdhanie Paul Tomblin Paul Tomblin k 56 56 gold badges silver badges bronze badges. As a follow up, if I do not create an instance of the object but instead I call a public static function. Does it imply that this block is guaranteed to execute before this public function call? If you call a public static function of the class, then the class needs to be loaded first, so yes, the static initializer will execute first.

Unless it was class initialisation which indirectly called the code which is trying to use it. Circular dependencies and all that. Tom is right - it's possible to write something where one static initializer calls a static method before another static initializer is called, but my mind recoils at the thought so I never considered it. Sign up or log in Sign up using Google. Sign up using Facebook. Instance variables can be initialized in constructors, where error handling or other logic can be used.

To provide the same capability for class variables, the Java programming language includes static initialization blocks. Here is an example:. A class can have any number of static initialization blocks, and they can appear anywhere in the class body. The runtime system guarantees that static initialization blocks are called in the order that they appear in the source code. The advantage of private static methods is that they can be reused later if you need to reinitialize the class variable.

Normally, you would put code to initialize an instance variable in a constructor. There are two alternatives to using a constructor to initialize instance variables: initializer blocks and final methods. Initializer blocks for instance variables look just like static initializer blocks, but without the static keyword:.