Question

我的问题是我的值i1，i2和i3都显示错误，说我在尝试编译程序时没有初始化值。我以为我给了他们一个价值，但显然没有。这是我的代码，我确定这是一个快速修复，谢谢。

public class Project3

 {
    /**********************************************************************************
 * Method Name: main <br>
 * Method Purpose: To develop a program that prompts the user for test scores and calculates their average and displays their GPA and letter grade.
 * <br>
 *
 * <hr>
 * Date created: 10/16/2013 <br>
 * Date last modified: 10/16/2013 <br>
 * <hr>
 * @param String[] args - Command Line Arguments
 */
    public static void main(String[] args)
    {

     //------------------------------variables--------------------------------  
    int iMenuOption;

    int i1;
    int i2;
    int i3;

    Scanner kb = new Scanner(System.in);
    String strName;

    myInfo();

    createWelcomeMessage();

    System.out.print("\n\n");

    pressEnterToContinue();

    System.out.print("\n");

    clearScreen();

    iMenuOption = menuOption();

    while (!(iMenuOption == '1'))
        {
        System.out.print("\nUser option 1 to enter test scores\n\n");

        pressEnterToContinue();
        clearScreen();

        iMenuOption = menuOption();
        }


    if (iMenuOption == '1')
        {
            i1 = testScore();
            i2 = testScore();
            i3 = testScore();
        }
    else if (iMenuOption == '2')
        {
            System.out.print("Score 1: " + i1);
            System.out.print("Score 2: " + i2);
            System.out.print("Score 3: " + i3);
        }

    }


    public static double calcAverage(int i1, int i2, int i3)
    {
    double dAverage;

    Scanner kb = new Scanner(System.in);

    dAverage = ((i1 + i2 + i3)/3.0);

    return dAverage;
    }   //end calcAverage



    public static void createWelcomeMessage()
    {
        Scanner kb = new Scanner(System.in);

        String strName;
        System.out.print("What's your user name? ");
        strName = kb.nextLine();

        System.out.print("\nHello, " + strName + " this program is made to calculate the" +
        " averages of given test scores, display your letter grade, and the GPA of the scores.");






    }

    public static void pressEnterToContinue()
    {
        Scanner keyboard = new Scanner(System.in);
        System.out.print("\t Press Enter to Continue \n ");
        keyboard.nextLine();

    }           //end pressEnterToContinue


    public static void clearScreen()    
    {
        System.out.print("\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n");

    }           //end clearScreen

    public static int testScore()
    {
        int iTestScore;

        Scanner kb = new Scanner(System.in);


        System.out.print("Enter a test score: ");
        iTestScore = kb.nextInt();



        return (iTestScore);
    }

    public static int menuOption()
    {
        Scanner kb = new Scanner(System.in);

        String strInput;
        int iMenuOption;


        System.out.println("\n        Menu Options");

        System.out.println("\t----------------------");
        System.out.println("\t1. Enter Test Scores");
        System.out.println("\t2. Display Test Scores");
        System.out.println("\t3. Display Average");
        System.out.println("\t4. Display Letter Grade");
        System.out.println("\t5. Display GPA");
        System.out.println("\t6. Exit Program");
        System.out.println("\t----------------------");

        System.out.print("Select one of the options: ");

        strInput = kb.nextLine();
        iMenuOption = strInput.charAt(0);

        while (!(iMenuOption == '1' || iMenuOption == '2' || iMenuOption == '3' || iMenuOption == '4' || iMenuOption == '5' || iMenuOption == '6'))
        {
            System.out.println("Invalid selection");



    enter code here

    System.out.print("Select one of the options: ");



    enter code here

        strInput = kb.nextLine();
            iMenuOption = strInput.charAt(0);
        }`enter code here`









        return iMenuOption;


    }



    public static void myInfo()
    {
        String strName = "\t\tBob";         //My name
        String strClass = "\t\tCSCI ";              //The class info
        String strDate = "\t\t9/18/13";                     //The program's date
        String strAssignment = "\tQuiz4";                   //The assignment name

        System.out.println("Author:\t\t" + strName);
        System.out.println("Class:\t\t" + strClass);
        System.out.println("Date:\t\t" + strDate);
        System.out.println("Assignment:\t\t" + strAssignment);


    }

    public static char letterGrade(double dAverage)
    {
        char cLetterGrade;

        if (dAverage >= 90 && dAverage <= 100)
        {
        cLetterGrade = 'A';
        }
        else if (dAverage >= 80 && dAverage < 90)
        {
        cLetterGrade = 'B';
        }
        else if (dAverage >= 70 && dAverage < 80)
        {
        cLetterGrade = 'C';
        }
        else if (dAverage >= 60 && dAverage < 70)
        {
        cLetterGrade = 'D';
        }
        else
        {
        cLetterGrade = 'F';
        }
        return cLetterGrade;






    }
}

Answer 1

您的问题是您没有强迫用户在选项2之前从菜单中选择选项1.因此就编译器而言，“选项2”块可能会先运行;在这种情况下，您将使用这三个变量，它们确实不会被初始化。

我认为您需要重新考虑您的程序流程，以确定允许您的用户执行此操作是否真的有意义。

Answer 2

在方法内部，您必须初始化变量

int i1 = 0;
int i2 = 2;
int i3 = 3;

您可以在不初始化的情况下定义类/实例变量，但对于局部变量（内部方法），您必须初始化它们

public class{
 String globalVariable; //this is ok defining with out initializing

 public void method1(){
   int localVariable = 1; //you should initialize these if you are using them inside
 }

}

Java，包含在while语句中的if语句中未初始化的值错误

2 个答案: