java - What does static succeeded only by two curly brackets means?

What does static succeeded only by two curly brackets means?
Sorry for the beginner question. I tried to look for a tutorial on it, but couldn't find one.
This use of static as: static {}, is not clear for me. I found it being used by others heredeveloperWorks.
I thought it may be a multiline, or group, modifier and tried the code below, but other type modifiers give errors not like static.

public class MyClass {
private volatile int v1=0;

private final int v2=0;
private static int v3=0;
static {             <----- No error here.
    int i1=0;
    String s1="abc";
    double d1=0;
};
final {              <----- Error here.
    int i2=0;
    String s2="abc";

    double d2=0;
};
volatile {           <----- Error here.
    int i3=0;
    String s3="abc";
    double d3=0;
};
}

Answer

It is a static initializer block, which is used to initialize static members of the class. It is executed when the class is initialized.

Your example :

static {            
    int i1=0;
    String s1="abc";
    double d1=0;
};

makes no sense, since it declares variables that are only in scope until the execution of that block is done.

A more meaningful static initializer block would be :

static int i1;
static String s1;
static double d1; 

static {            

    i1=0;
    s1="abc";
    d1=0;
};

This example still doesn't justify using a static initializer, since you can simply initialize those static variable when you declare them. The static initializer block makes sense when the initialization of static variables is more complex.