錯誤：變量可能尚未初始化和if語句

Question

所以基本上

 //Black ops 2 Class generator Please help me FIX!!!!!!
    import java.util.Scanner;
    import java.util.Random;
    public class money
        {
        public static void main(String[]args)
            {
        String primaryOption;
        Scanner scan = new Scanner (System.in);
        Random primaryGen = new Random();

        String weaponType; //Rifle, SMG, HMG, Sniper, shotgun, or special
        String primaryoption; //Do you want a primary?
        String primaryWeapon; //The gun you get
        int primaryWeapon1; 
        String primrayCamo; //Camo for primary
        String MTAR = "MTAR", Type25 = "Type 25", SWAT556 = "SWAT-556", FALOSW = "FAL-OSW", M27 = "M27", SCARH = "SCAR-H", SMR = "SMR", M8A1 = "M8A1", AN94 = "AN-94";

        String secondaryOption; //Do you want a secondary?
        String secondaryWeapon; //Your gun
        int secondaryWeapon1;
        String secondaryCamo; //Camo for secondary
        System.out.println("Would you like a Primary Weapon? Yes(1) or No(2)");
        primaryOption = scan.nextLine();
            if (primaryOption.equals("Yes")) {
                System.out.println("Would you like a Rifle, SMG, HMG, Sniper, Shotgun, or Special?)");
                weaponType = scan.nextLine();
                    if (weaponType.equals("Rifle")) {
                        primaryWeapon1 = primaryGen.nextInt(1) +1;
                        if (primaryWeapon1 == 1) {
                            primaryWeapon = MTAR; //*&%&*This is where i initialized it.
    }
                return; 

                            }
    System.out.println("Primary Weapon: " + primaryWeapon); //This is where the error is. It say's im not initializing the variable but I initialize it in the last if statement
    }
    }
    }

Answer 1

它說我不是在初始化變量，而是在最后的if語句中初始化它

如果沒有執行“ if”塊，會發生什么？ 那么該變量將被取消分配，對嗎？ 這就是為什么編譯器抱怨。

應該在所有可能的流程中分配局部變量，否則是編譯時錯誤。

Answer 2

您必須先初始化變量，然后才能使用它。 如果if語句失敗，則此變量將保持未初始化狀態：

 System.out.println("Primary Weapon: " + primaryWeapon); 

因此，在聲明它的地方，將其等於"" ：

String primaryWeapon = ""; //The gun you get

Answer 3

在某些情況下， PrimaryWeapon永遠不會初始化（只要PrimaryWeapon1不等於1 ）。

使用它，它是固定的：

String primaryWeapon = "";

Answer 4

我認為您的問題在於if語句：假設您到達此處，而武器類型確實等於“步槍”，它將返回並退出您的函數。 您應該將primaryWeapon初始化為默認值，即primaryWeapon =“ None”;

 if (weaponType.equals("Rifle")) {
                        primaryWeapon1 = primaryGen.nextInt(1) +1;
                        if (primaryWeapon1 == 1) {
                            primaryWeapon = MTAR; //*&%&*This is where i initialized it.
                        }
                        return; //<---- remove this
 }

同時完成if塊， if(yes) {...} else {...}. Java編譯器將分支出條件子句，並在嘗試使用非初始化變量時發出警告/錯誤。 例如：

int b;
boolean f = true;
if(f)
    b =1;
System.out.println(b); //error because no else block


//Fixed
int b; 
boolean f = true;
if(f)
b = 1;
else
b= 2;
System.out.println(b);

-尼魯