如何在if语句中声明值？ （在Java中）

Question

So this is what i have so far and i have no clue why the program is not responding the way i want it to. Keeps showing up that "avg2 might not have been initialized". Any ideas??

if (a < b && a < c) {
    System.out.println("The lowest score was: " + a);
    System.out.println("The average without the lowest score is: " + ((b + c) / 2));
    avg2 = ((b + c) / 2);
}

if (b < a && b < c) {
    System.out.println("The lowest score was: " + b);
    System.out.println("The average without the lowest score is: " + ((a + c) / 2));
    avg2 = ((a + c) / 2);
}

if (c < a && c < b) {
    System.out.println("The lowest score was: " + c);
    System.out.println("The average without the lowest score is: " + ((a + b) / 2));
    avg2 = ((a + b) / 2);
}

Answer 1

I suppose you have declared avg2 like this: double avg2; with no initial value. The problem is that if a == b == c for example, none of your if conditions will be true and avg2 will not be initialised.

• Solution 1: initialise avg2: double avg2 = 0;
• Solution 2 (better): instead of a succession of ifs, use an if / else if / else syntax. If there is an else, the compiler will be satisfied that avg2 will always be initialised.

Answer 2

The problem is that it appears to the compiler as though there is a possible route through the code in which none of the if statement conditions are met. If that is the case, then no assignment will ever be made to avg2 .

Answer 3

Because compiler cannot know that one of the if conditions will evaluate to true and therefor avg2 would have been assigned. One work around is to put an unconditional else :

if (c < a && c < b) {
 ....
} else {
   throw new RuntimeException("Cannot be here");
}

// now use can use avg2 here

Answer 4

To fix the 'not initialized' error you should rearrange your 3 if statements into one if-else block. The compiler isn't going to test whether the condition for an if statement will be true or not, but if you assign your variable inside each part of the if-else block (which must include the "if all else fails" else), it would be inevitably initialized.

double avg2;
if (a < b && a < c)
{
    System.out.println("The lowest score was: " + a);
    System.out.println("The average without the lowest score is: " + ((b + c) / 2));
    avg2 = ((b + c) / 2);
}else if (b < a && b < c)
{
    System.out.println("The lowest score was: " + b);
    System.out.println("The average without the lowest score is: " + ((a + c) / 2));
    avg2 = ((a + c) / 2);
}else {
    System.out.println("The lowest score was: " + c);
    System.out.println("The average without the lowest score is: " + ((a + b) /2));
    avg2 = ((a + b) / 2);
}

A better way to perform this procedure:

double avg2;
double lowest = a;
if(lowest > b)
    lowest = b;
if(lowest > c)
    lowest = c;
System.out.println("The lowest score was: " + lowest);
avg2 = (a + b + c - lowest)/2;
System.out.println("The average without the lowest score is: " + avg2);

Answer 5

That code has hurt my eyes so much, that I felt obliged to post this answer :)

double lowest = Math.min(Math.min(a, b), c);
double avg2 = (a + b + c - lowest) / 2;
System.out.println("The lowest score was: " + lowest);
System.out.println("The average without the lowest score is: " + avg2);

Just 4 lines instead of 15, and this code will not generate that warning because variables are being initialized.

Probably the warning is because the variable is being initialized inside an if statement, which eventually may not occur...