Eclipse，無法初始化局部變量

Question

我已經在這個程序上工作了幾天，並且應該在今晚的午夜。 我一輩子都無法弄清楚為什么我總是收到“無法初始化局部變量”錯誤的原因。 這是我的第一門編碼課，我不太了解。 如果有人可以通過解釋修復程序來幫助我，以及為什么繼續發生此錯誤，那將是很好的。

我將“ **”放在錯誤所在的位置（接近代碼結尾）。 任何幫助將是巨大的！ 提前致謝。

/*This program will determine how much the students 
tuition and fees are based on location and classes. It will return the
total tuition, fees, and combined total */
import java.text.DecimalFormat;
import java.util.*;

public class Project2 {

public static void main(String[] args) {
    Scanner in=new Scanner(System.in);

    //Declaring variables and decimal format
    int TotalHours;
    int Price;
    int CreditCharge;
    int CITFee;
    int OnlineFee;
    int INFCSCFee;
    int TotalTuition;
    int TotalFee;
    int TotalCombined;
    DecimalFormat df = new DecimalFormat("$#,###");


    //Getting the students First name, Last name, and Date
    System.out.print("Enter your first name: ");
    String FirstName = in.nextLine();
    System.out.print("Enter your last name: ");
    String LastName = in.nextLine();
    Date d = new Date ( );


    //Getting the state of residency. If in Ohio, asking the user if they are Metro
    System.out.print("Enter your State of residency as a 2-letter abbreviation: ");
    String State = (in.next().toLowerCase());

    if (State.equals ("oh") || State.equals("OH")){
        System.out.print( "Are you a Cincinnati resident? (Y/N) ");
        String Metro = in.next();    
        if (Metro.equals ("y")) Price = 567;    
        }
    else Price = 750;

    if (State.equals ("ky") ){ Price = 375; 
        }
        else if (State.equals ("in")){Price = 375;  
        }
        else {Price = 750;
        }       

    //Getting the number of credit hours the student is taking
    System.out.print("Enter the total credit hours for the upcoming semester: ");
     TotalHours = in.nextInt();

    if (TotalHours <= 12) CreditCharge = (TotalHours * Price);

    else {CreditCharge = (Price * 12);
    }    

    //Getting the number of CIT hours the student is taken
    System.out.print("Enter the total of CIT credits you are taking: ");
    int TotalCITHours = (int) in.nextInt();
    CITFee = (TotalCITHours * 40);

    //Getting the number of online credit hours the student is taken
    System.out.print("Enter the total number on-line credit hours you are         taking: ");
    int OnLine = (int) in.nextInt();
    OnlineFee = (OnLine * CITFee * 35);

    //Seeing if the student is taken either INF 120 or CSC 260 
    System.out.print("Are you taking either INF 120 or CSC 260? (Y/N) ");
    String INFCSC = in.next().toLowerCase();
    if (INFCSC.equals ("y")) INFCSCFee = (char) (CITFee * OnlineFee + 60);

    //Calculating the tuition, fees, and total combined.
    **    TotalTuition = CreditCharge;
    **    TotalFee = INFCSCFee;
    **    TotalCombined = TotalTuition + INFCSCFee;       

    //Tuition Statement for FirstName, LastName, Date
    System.out.println("\nTuition Statement for " + FirstName + LastName);
    System.out.println(d);
    System.out.println("Tuition: " + df.format (TotalTuition) );
    System.out.println("Fees: " + df.format(TotalFee));
    System.out.println("Total: " + df.format(TotalCombined));

    }

}

Answer 1

如果變量INFCSCFee對問題“您是否服用INF 120或CSC 260？ 如果變量尚未初始化，Eclipse將不允許您運行程序。 在代碼的頂部

int INFCSCFee;

替換為

int INFCSCFee = 0;

或在其他地方或使用其他一些值初始化變量。

Answer 2

這是錯

    if (INFCSC.equals ("y")) INFCSCFee = (char) (CITFee * OnlineFee + 60);

這是可以初始化INFCSCFee的唯一位置。 因此，有可能在使用之前尚未對其進行初始化。 更一般而言，這是不允許的：

int x; // declare x - not yet initialised
if (someCondition)
   x = 3; // initialise to 3
// if somecondition was false, x is still unitialised
System.out.println("x is "+x); // Error

您不能使用在方法中聲明的變量，除非編譯器可以確保在您使用之前已對其進行了初始化。 這將被允許：

int x; // declare x - not yet initialised
if (someCondition)
   x = 3;
else if (somethingElse)
   x = 4;
else
   x = 5;

// For all outcomes, x has been initalised, so it is safe to use
System.out.println("x is "+x);

這也是允許的：

int x; // declare x - not yet initialised
if (someCondition)
   x = 3;
else
   return;

// Although someCondition may have been false, if we reach this line of
// code, it is because someCondition was true and therefore x was initialised
System.out.println("x is "+x); // will print x is 3

最后，您可以在聲明時初始化變量：

int x = 0;

現在，無論在何處使用x，都將確保它被初始化，因此不會出現編譯錯誤。 這不一定是一件好事，因為該編譯器錯誤實際上可能會向您顯示代碼中的錯誤，並且您通過為變量提供默認值來抑制了它。