Czemu ten kod nie działa tak samo jak ten z else itp.?

Pytania dotyczące zadania

Mniejsza z dwóch liczb

Składnia Java, Poziom 2, Lekcja 8

Dyskutowane

package pl.codegym.task.task02.task0214; /* Mniejsza z dwóch liczb */ public class Solution { public static int min(int a, int b) { //tutaj wpisz swój kod if (a <= b) return a; if (b <= a) return b; } public static void main(String[] args) throws Exception { System.out.println(min(12, 33)); System.out.println(min(-20, 0)); System.out.println(min(-10, -20)); } }

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owlek Java Developer

29 listopada 2023, 00:44

Twoja metoda nie zwraca żadnej wartości jeśli oba przypadki if'a będą false, a musi. Bez znaczenia, że pokryłeś wszystkie przypadki, taka jest zasada metod.

Guadalupe Gagnon

Poziom 37 , Tampa, United States

28 listopada 2023, 19:32

A computer has no ability to think and thus is governed by rules. One rule is that when a method has a return value then it MUST have at least one viable path to a return statement. The code you shared has 2 return statements that are behind logic gates (the 'if' statements) which is illegal code and will not compile until it has been fixed. It does not matter if the logic gates cover all possibilities, it is still illegal to do this. Loops are also logic gates for this purpose. The code would work as an if-else because the else provides a guaranteed path to a return statement in the case that the if statement is false. So, this first example below is invalid because the return statements are all behind logic gates. This breaks the rule that there needs to be a viable path to a return statement:

// THIS IS INVALID CODE
if (/*some boolean check*/)
   return a;

if (/*some other boolean check*/)
   return b;

This next example is valid because it will return 'a' if the boolean check is true, otherwise return b. Therefore a viable path exists to a return statement.

// THIS IS VALID CODE
if (/*some boolean check*/)
   return a;
else
   return b;

This is also valid because it will return 'a' if the boolean check is true, otherwise return b. It is functionally identical to the above example.

// THIS IS ALSO VALID CODE
if (/*some boolean check*/)
   return a;

return b;

And last, this is also invalid because the loop is a logic gate and the return statements are inside of it leaving a guaranteed viable path not reachable.

// THIS IS INVALID CODE
while(/*boolean check*/) {
   if (/*boolean check*/)
      return a;
   else
      return b;
}