Hello, dear ppl; I just tried to solve my task, but the compiler gave me an error. So, I have two questions for two cases.

Frage zur Aufgabe

Gelöst

The first question refers to my solution which appears at the very bottom, the second refers to the screenshot I've attached. 1. Can't I declare and initialize variables in the body of the if-clause and for the case I can't, why is this? 2. In the screenshot I see my alternative approach. There I was declaring the variable before the if clauses, in the body of the method itself, and then I am initializing the variables in the bodies of the if-clauses. There, the compiler said that the variable might not get initialized. But in my understanding, one of the cases regarding the if clauses will be picked necessarily, so that the variable gets initialized anyhow. Am I wrong about this?

Schreibe eine Funktion, welche die kleinste aus drei Zahlen berechnet.

Hinweis:
Du musst den Rumpf der bestehenden Funktion min schreiben.

Anforderungen:

Das Programm muss Text auf dem Bildschirm ausgeben.
Die Methode min darf keinen Text auf dem Bildschirm anzeigen.
Die Methode main muss die Methode min viermal aufrufen.
Die Methode main muss das Ergebnis der Methode min anzeigen. Der Satz soll jedes Mal in einer eigenen Zeile stehen.
Die Methode min muss die kleinste Zahl aus den Zahlen a, b und c zurückgeben.

package de.codegym.task.task02.task0216; /* Die kleinste aus drei Zahlen */ public class Solution { public static int min(int a, int b, int c) { // int kleinsteZahl; if(a <= b && a <= c) int kleinsteZahl = a; else if (b <= a && b <= c) int kleinsteZahl = b; else if (c <= a && c <= b) int kleinsteZahl = c; return kleinsteZahl; // int m1 = a < b ? a : b; // int m2 = m1 < c ? m1 : c; // return m2; } public static void main(String[] args) throws Exception { System.out.println(min(1, 2, 3)); System.out.println(min(-1, -2, -3)); System.out.println(min(3, 5, 3)); System.out.println(min(5, 5, 10)); } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

15 Februar 2023, 15:02

Lösung

#1 Variables are only useable in the block of code that they are declared in, and any block of code within that block. A block of code is anything between open and closing curly brackets. It is best practice to indent code by one each new block of code (which you did) as it is easier to quickly see where blocks of code are. An 'if' statement is declared like this:

if( /*boolean*/ ) {
   // block of code
}

When the if statement is true the code in the following block of code will be executed. There is a special case with if statements (and loops) where if you have 1, and only 1, line of code in the block that follows then you do not need curly brackets, such as the case with your attached code. In this case the brackets are implied to be there and variables that are declared are still only useable only in that block. Since the block is only 1 line of code it typically is a bad place to be declaring variables.

Guadalupe Gagnon

Level 37 , Tampa, United States

15 Februar 2023, 15:19

Lösung

#2 For a variable's value to be used on any line of code that variables MUST have the value initialized in a prior line of code. Having the values initialized behind logic gates, such as if statements, does not guarantee that they will be initialized.... even if you are absolutely positive that you covered every possible outcome. I can look at the code from your alternative approach and see that every possible outcome is covered in your three if statements. You and I can determine this because we possess the ability to reason that a computer does not possess. To fix this you can set a default value to your variable when you declare it, or you need a default condition to you if statements that guarantee a value being set. So either do this:

// default value
int kleinsteZahl = c;

if(a <= b && a <= c)
   kleinsteZahl = a;
else if (b <= a && b <= c)
   kleinsteZahl = b;

or this:

int kleinsteZahl;

if(a <= b && a <= c)
   kleinsteZahl = a;
else if (b <= a && b <= c)
   kleinsteZahl = b;
else  // default statement
   kleinsteZahl = c;

Andreas Blank

Level 8 , Germany, Germany

23 Februar 2023, 12:21

Thanks for the answers that helped a lot :)