Question

I know how a static init block works.
Can anyone please tell me some typical uses of it.

Answer 1

When you want to initialize one or more static variables in one place

It is useful, because you can apply exception handling, which is not possible with the in-line initialization.

For example:

public static ImageIcon defaultIcon = ImageIO.read(..);

can be initialized with

public static ImageIcon defaultIcon;
static {
   try {
       defaultIcon = ImageIO.read(..);
   } catch (IOException ex){
     System.out.println("No default icon available");
   }
}

Another application is complex initialization. For example, if an item requires more than one line of code to be initialized. Let’s say you have a configuration:

public static Configuration configuration;
static {
     confuguration = new Configuration();
     configuration.setSomething(..);
     configuration.setSomethingElse(..);
     ...
}

A third usage is to initialize some external API infrastructure. One example from my current project:

static {
    org.apache.xml.security.Init.init();
}

But, as Mykola Golubyev noted, static initialization blocks make code less readable, so use them with caution. static methods do the same thing more transparently.