我在下面的 java 程序中收到错误：未声明的变量：IO，但据我所知代码是正确的

Question

       public class CourseGrade {
public static void main(String[] args) {
    int examWeight = 70;
    int labWeight = 20;
    int hwWeight = 10;
    double examScore;
    double labScore;
    double hwScore;
    double finalScore;
    
    //ask Student to input scores for exam, lab, hw
    IO.output("Enter your exam scores: ");
    examScore = IO.inputDouble();
    IO.output("Enter your lab scores: ");
    labScore = IO.inputDouble();
    IO.output("Enter your homework scores: ");
    hwScore = IO.inputDouble();
    
    //compute final score as the weighted sum of exam, lab, hw score
    examScore = examScore * (examWeight / 100);
    labScore = labScore * (labWeight / 100);
    hwScore = hwScore * (hwWeight / 100);
    
    finalScore = examScore + labScore + hwScore;
    
    // output the final score
    IO.outputln("Your final score is: "+ finalScore);
}

} 我一次又一次收到此错误：未声明的变量：IO，并且此解决方案问题在网络上不可用 我在 java 的 bluej 编辑器中运行这段代码 根据我的 io 部分只与语法有关

Answer 1

您需要 IO 类，其中包含多种方法来运行您的代码。 IO 类可能看起来像这样：

public class IO {
    
    private static java.util.Scanner userIN = new java.util.Scanner(System.in);
    
    public static void output(Object input) {
        System.out.print(input);
    }

    public static void outputln(Object input) {
        System.out.println(input);
    }
    
    public static void outputf(String input, Object[] varArgs) {
        System.out.printf(input, varArgs);
    }
    
    public static String inputLine() {
        return userIN.nextLine();
    }
    
    public static String inputToken() {
        return userIN.next();
    }
    
    public static int inputInt() {
        int i = userIN.nextInt();
        userIN.nextLine(); // Consume ENTER key.
        return i;
    }
    
    public static long inputLong() {
        long i = userIN.nextLong();
        userIN.nextLine(); // Consume ENTER key.
        return i;
    }
    
    public static double inputDouble() {
        double i = userIN.nextDouble();
        userIN.nextLine(); // Consume ENTER key.
        return i;
    }
    
    public static float inputFloat() {
        float i = userIN.nextFloat();
        userIN.nextLine(); // Consume ENTER key.
        return i;
    }
    
    public static void inputClose() {
        userIN.close();
    }

    // Add more methods as required....
}

与你的代码一起使用：

public static void main(String[] args) {                                          
    int examWeight = 70;
    int labWeight = 20;
    int hwWeight = 10;
    double examScore;
    double labScore;
    double hwScore;
    double finalScore;

    //ask Student to input scores for exam, lab, hw
    IO.output("Enter your exam scores: ");
    examScore = IO.inputDouble();
    IO.output("Enter your lab scores: ");
    labScore = IO.inputDouble();
    IO.output("Enter your homework scores: ");
    hwScore = IO.inputDouble();

    //compute final score as the weighted sum of exam, lab, hw score
    examScore = examScore * (examWeight / 100d);
    labScore = labScore * (labWeight / 100d);
    hwScore = hwScore * (hwWeight / 100d);

    finalScore = examScore + labScore + hwScore;

    // output the final score
    IO.outputln("Your final score is: " + finalScore);
}