When all the required work can be done inside the constructor, then why do we still need non-static block in Java?

EDIT: What about normal classes for which non-static blocks run everytime before the constructor?

解决方案

In additional to @Bohemian's answer.

If you have multiple constructors an intialiser block avoid duplication.

public class A {

final Map map = new HashMap(); {

// put things in map.

}

final int number; {

int number;

try {

number = throwsAnException();

} catch (Exception e) {

number = 5;

}

this.number = number;

}

public A() { /* constructor 1 */ }

public A(int i) { /* constructor 2 */ }

}

What about normal classes for which non-static blocks run everytime before the constructor?

Technically the order is

the super constructor is always called first

all the initializer blocks in order of appearence.

the constructor code

In reality all this code is in the byte code for each constructor so there is nothing before or after the constructor at runtime.

Before there is any more confusion as to the order of initialization

public class Main extends SuperClass {

{

System.out.println("Initialiser block before constructor");

}

Main() {

System.out.println("Main constructor");

}

{

System.out.println("Initialiser block after constructor");

}

public static void main(String... args) {

new Main() {{

System.out.println("Anonymous initalizer block");

}};

}

}

class SuperClass {

SuperClass() {

System.out.println("SuperClass constructor");

}

}

prints

SuperClass constructor

Initialiser block before constructor

Initialiser block after constructor

Main constructor

Anonymous initalizer block