When is the static block instantiated in a Java Class

Question

Suppose there is a static block in a Class

public class Menu {

    private static Map<String, String> buttonEventMap = new HashMap<String, String>();

    static {
        buttonEventMap.put("show-user","show");
        buttonEventMap.put("delete-user","delete");
    }

    public static Map<String, String> getHashMap() // To get the hash map
}

what is the life cycle of the block, when it will be instantiated, when the program starts or when we create the first object of the Class

http://stackoverflow.com/questions/2007666/in-what-order-do-static-initializer-blocks-in-java-run and http://stackoverflow.com/questions/2943556/static-block-in-java — alain.janinm, May 29 '12 at 09:21
A static initializer declared in a class is executed when the class is initialized (JLS - http://docs.oracle.com/javase/specs/jls/se7/html/jls-8.html#jls-8.7) — KV Prajapati, May 29 '12 at 09:23
Take a look at the comment by Dalee Bisen on http://www.jusfortechies.com/java/core-java/static-blocks.php — Insectatorious, May 29 '12 at 09:25

JB Nizet · Answer 1 · 2012-05-29T09:41:34.793

6

It's executed when the class is initialized by the class loader. And the class is initialized lazily, the first time some code in the application needs this class (to call a static method, or to reference one of its static fields, or to create a new instance for example).

So if the program never uses the class, the static block will never be executed.

edited May 29 '12 at 09:41

answered May 29 '12 at 09:18

JB Nizet

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A fully precise statement is that it's executed when the class is **initialized**. Class loading can occur at any time the implementation sees fit, whereas class init must happen at the precise moment defined by the JLS. – Marko Topolnik May 29 '12 at 09:37

score 2 · Answer 2 · answered May 29 '12 at 09:16

2

When you first access the class in your application.

answered May 29 '12 at 09:16

Jouni Aro

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Access means when we create the first object of the class ? – Isuru May 29 '12 at 09:19
Yes typically. JB Nizet answered this already more completely. – Jouni Aro May 29 '12 at 09:20

When is the static block instantiated in a Java Class

2 Answers2