Using Instance Blocks in Java

The instance block can be defined as the name-less method in java inside which we can define logic and they possess certain characteristics as follows. They can be declared inside classes but not inside any method. Instance block logic is common for all the objects. Instance block will be executed only once for each object during its creation. 

Illustration:

class GFG {
    {
        // Code inside instance block
    }
}

The advantage of the Instance block is as follows: 

Instance blocks are executed whenever an object of any kind is created. If we want to write a logic that we want to execute on the creation of all kinds of objects, then using instance blocks is a good idea to avoid writing the same logic inside every constructor.

The drawback of the Instance block is as follows: 

We generally don’t use them for the initialization of objects because they can not accept the parameters. If we still use instance blocks for the purpose of initialization, then all the objects will have to be initialized with the same values which are practically useless.

Example 1:

Instance block
1st argument constructor
Instance block
2nd argument constructor
Instance block
3rd arguments constructor

Note: The sequence of execution of instance blocks follows the order- Static block, Instance block, and Constructor.\\

It can be justified from the example been proposed below as follows:

Example 2:

I am Static block!
I am Instance block!
I am Constructor!