Initializing a java array

Question

Recently, I found that an array can be initialize as follows:

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?

Answer 1

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.

Answer 2

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