Why does this variable need an integer value when initiated for the code to work?-CodePudding

The following question states:

"Write a loop that reads positive integers from standard input and that terminates when it reads an integer that is not positive. After the loop terminates, it prints out, on a line by itself, the sum of all the even integers read. Declare any variables that are needed. ASSUME the availability of a variable, stdin, that references a Scanner object associated with standard input".

The answer is as follows:

int even = 0;
int i = 1;
while (i > 0){
i = stdin.nextInt();
if ((i % 2)==0 && (i > 0)){
even  = i;
}
}
System.out.print(even);

Why does the int variable "i" need to be set to a numerical value for the code to work? I can't seem to figure out why.

CodePudding user response：

int i;
while (i > 0){

Looking at these lines -- just these lines, nothing else -- should the while loop run, or not?

There's no way to tell without setting i.

CodePudding user response：

Why does the int variable "i" need to be set to a numerical value for the code to work? I can't seem to figure out why.

Your local variable 'i' has to be initialized at least one line before it is used, because otherwise you'd be attempting to access a memory cell that has not been initialized, and since Java does not allow you to access the previous content of a memory cell, it'll give you a compile error.

While not recommended, you can leave a variable uninitialized, but you'll have to initialize it at least one line before using it.

Another solution, if for some reason you don't want to initialize 'i', is to use a do-while loop instead of a while-loop:

int even = 0;
int i;
do {
    i = stdin.nextInt();
    if ((i % 2)==0 && (i > 0)){
        even  = i;
    }
} while (i > 0)
System.out.print(even);