Thread: Adding the "final" keyword makes difference, I'm confused with the sequence flow.

Codes:

class Parent {
	protected int value = 1 ;	
	Parent() { 
            value = getNum();
        }	
	public int getNum(){ 
            return 5; 
        }	
	public int getValue(){ 
            return value; 
        }
}
 
class Child extends Parent {
   private int x = 4;     // Before line is executed, the value of "Parent.value" already assigned to be 10, why?
   private final int num = 10; //Remove the "final" here, result totally changed, why?
 
   public Child(){}
 
   public int getNum(){ 
      return num;  
   }
}
 
public class test
{
  public static void main(String args[])
  { 
      Child cObj = new Child();
      System.out.println("cObj.getValue() = " + cObj.getValue());
  }
}

Remove the "final" keyword from the line "private final int num = 10;", the result prints out "cObj.getValue() = 0". I noticed that the Parents.value is assigned to 0 before Child.num is initialized to be 10 of the line "private final int num = 10;"; Strange....

With the "final", runs with break point and breaks on line, private int x = 4;, the Parents.value is already assigned to 10, why is that?

By running the program with "final" and without "final" using break point, the line of the code in sequence flow will be different?

Also, I noticed the sequence flow will run differently when Parent.value is initialized and not initialized.
I am very confused with the code traveling sequence, can anyone please explain that to me in very detail ?

The first call in a child class is to call the parent class constructor, initialization of non-final variables sets their values to default, and initialization to custom values occurs inherently within the constructor (see Initializing Fields (The Java™ Tutorials > Learning the Java Language > Classes and Objects) ). In affect, although not explicit this results in the following for a non-final variable (this might help you work out the workflow)

class Child extends Parent {
   private int num;//defaults to 0 
 
   public Child(){
       super();
       num = 10;
   }
 
   public int getNum(){ 
      return num;  
   }
}

Adding final for initialization results in initialization of the variable prior to the constructor to a value different than the default value for the variable type. See the following article for a more thorough description
Object initialization in Java - JavaWorld