error?

[Ankur kothari]

  class Forward
{
 {
        i = 10;
    }
    
    int i = 5;

}  

above code compiles wheres this doesnt

  class Forward
{

        i = 10;
    
    
    int i = 5;

}
  

[Sonali Sehgal]

 
 class MyClass
{   
 {     i = 10;      }   //Instance Block
       
    int i = 5;   
  

   

In this code during the execution of the program first the compiler declares and intializes the variable and then after that the instance block executes.

   

 class MyClass
{   
      i = 10;      
       
    int i = 5;   
}
  
 

In the above code the variable i is not even declared whether it is an integer ,float or what it is whereas on the first code we are declaring it.Hence it will give your a compile time error of identifier expected.

[Ankur kothari]

then why is there an error in this?
class Forward
{
{
System.out.println(i);
i = 10;

}

int i = 5;


}

isnt i already declared when it reaches system.out?

[Ankit Garg]

Ankur, please UseAMeaningfulSubjectLine for your topics.

Do you think this will compile

class Whatever {
    System.out.println("nothing");
}

You can't have anything other than method declarations (including constructors), variable/constant declaration and static and instance initializer blocks in your class body...

[Sonali Sehgal]

   
class MyClass
{ 

{
//System.out.println(i); //1
System.out.println(this.i); //2
i = 10; //3
 
} 

int i = 5; 
public static void main(String...arga)
{
new MyClass();
}

} 


 

This System.out gives you an error because it is not the correct forward referencing to correct this you have to use this.i so it specifically points to the reference variable and gives the output.

Well, in the case of forward referencing, we're not trying to read from i, we're assigning a value to it. Therefore, there's no "dangerous" operation occurring here and the compiler allows it. For more information check this link of java ranch I hope it will make it more clear...



Webpage for Forward Referencing

[Punit Singh]

Use java decompiler to get the idea how forward ref is resolved by compile, what compiler is doing internally. How code are placed in the last and executed.