java - What's the difference between an instance initializer and a constructor?

Question

Just wondering about the reason of compiling code like this:

class MyClass extends AnotherClass {
  {
    MySecondClass object = new MySecondClass();
    object.doSomething();
  }
}

Whats the difference between this code and code in constructor? This code executes before the object creation.

Answer 1

The code inside the braces with no names will be part of the constructor of the class and be executed before the logic contained in the class constructor.

Quick example:

public class Foo {
    {
        System.out.println("Before Foo()");
    }

    public Foo() {
        System.out.println("Inside Foo()");
    }

    {
        System.out.println("Not After Foo()");
    }
}