help on another strange question.

[david hu]

Why can program 1 work, but program 2 cannot?
Program1:
-------------------------
public class OuterTest{
public static void main(String args[]){
OuterTest test = new OuterTest();
test.processBoolean(false);
}
void processBoolean(boolean flag)
{
final int x;
if (flag){
x =9;
System.out.println(x);
}
else{
x=7;
System.out.println(x);
}
}
}
program 2:
_________________________
public class OuterTest{
public static void main(String args[]){
OuterTest test = new OuterTest();
test.processBoolean(false);
}
void processBoolean(boolean flag)
{
final int x;
if (flag){
x =9;
System.out.println(x);
}


if (!flag){
x = 27;
System.out.println(x);
}
}
}

[Namrata Shetty]

i think the compiler expects an 'else' statement

[Guoqiao Sun]

Well, for final variables, you should always initialise it before using it. If the declaration and initialisation are not in the same statement, the compiler will make sure that you initialise it properly, otherwise it complains.
The point is that the kind CHECK that the compiler gave is simple one, like <code>if(){} else{}</code>, it will not check relatively complex logic, like case 2.
Correct me if i am wrong, hope it helps.
Guoqiao

[Padmaja Balaji]

The compiler error goes like this :
Can't assign a second value to a blank final variable: x
x=7;
My understanding of the subject is :
- if...else is used when u want either this or that (so you have only one option).
- two ifs can be used for two different cases.
- the modifier used for 'x' is final. If a final variable (in other terms 'constant') may not be modified once it has been assigned a value. In this case, final variable is already assigned a value of 9. A second value of 7 will not be acceptable to 'x'. Hence the error.
- Either use if....else in the program or remove the final modifier and the output will be 7.
Am I right?
- Paddy

[Asif Masood]

Hi,
As it is said that final variables should be declared and initialized in one line OR final varible should be initialized before using it and ONE MORE THING which is important here for this question that is the value of the final variable can not be changed once assigned. We are violating this rule here in this program by assigning the value to final varible in both if statements (CASE 2) because both the if statements are independant and compiler does not know at compile time that wether one or both will execute that's why it objects that the final variable is being initialzed twice. While in CASE 1, compiler knows by the combination of if, else that only one block will be executed that's why it does not give error in that case.
Hope this explanation will clear all doubts.
Asif Masood