Initializing a java array

Recently, I found that an array can be initialize as follow开发者_开发知识库s:

private static int[] _array = new int[4];

// An arbitrary amount of code

{ 
    _array[0] = 10;
    _array[1] = 20;
    _array[2] = 30;
    _array[3] = 40;
}

What is this form of initialization called? What are its limitations?

This is instance member initialization using an initializer block, and it looks a lot like static initialization which would prefix that block with the word static.

Its limitations would match that of any constructor as the Java compiler copies initializer blocks into every constructor. Therefore, this approach can be used to share a block of code between multiple constructors.

It is initialization block and regarding to documentation:

The Java compiler copies initializer blocks into every constructor. Therefore, this approach can be used to share a block of code between multiple constructors

I've answered yesterday in similar post here