我做了这个计算器应用，是为了在我的APCSA课程中计算墙面需要的油漆量，或混凝土板上的厚度。不过，当我尝试运行它时，遇到了这个错误信息

error: Class names, 'MaterialsCalculatorApp.Java', are only accepted if annotation processing is explicitly requested.

有人能弄清楚怎么修复吗？

下面是代码，供参考（我们这节课还没学过Javac）。

MaterialsCalculatorApp.Java
import java.util.Scanner;

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

        System.out.println("===== Materials Calculator =====");
        System.out.println("1. Paint Wall");
        System.out.println("2. Concrete Slab");
        System.out.print("Choose project type (1 or 2): ");

        int choice = sc.nextInt();

        MaterialProject project = null;

        if (choice == 1) {
            project = new PaintWallProject();
        } else if (choice == 2) {
            project = new ConcreteSlabProject();
        } else {
            System.out.println("Invalid choice.");
            sc.close();
            return;
        }

        project.collectInput(sc);

        double materialNeeded = project.calculateMaterialNeeded();

        System.out.println("\n----- RESULTS -----");
        System.out.println("Project Type: " + project.getName());
        System.out.printf("Material Needed: %.2f %s\n",
                          materialNeeded,
                          project.getUnit());

        double cost = project.calculateEstimatedCost(materialNeeded);

        System.out.printf("Estimated Cost: $%.2f\n", cost);

        sc.close();
    }
}

MaterialProject.java
import java.util.Scanner;

public abstract class MaterialProject {

    private String name;
    private String unitLabel;
    private double costPerUnit;

    public MaterialProject(String name, String unitLabel, double costPerUnit) {
        this.name = name;
        this.unitLabel = unitLabel;
        this.costPerUnit = costPerUnit;
    }

    public String getName() {
        return name;
    }

    public String getUnitLabel() {
        return unitLabel;
    }

    public double getCostPerUnit() {
        return costPerUnit;
    }

    public abstract void collectInput(Scanner sc);
    public abstract double calculateMaterialNeeded();

    public double calculateEstimatedCost(double amountNeeded) {
        return amountNeeded * costPerUnit;
    }
}

PaintWallProject.java
import java.util.Scanner;

public class PaintWallProject extends MaterialProject {

    private double width;
    private double height;
    private int coats;

    private static final double COVERAGE = 350.0; // sq ft per gallon

    public PaintWallProject() {
        super("Paint Wall", "gallons", 34.99);
    }

    @Override
    public void collectInput(Scanner sc) {
        System.out.print("Enter wall width (feet): ");
        width = sc.nextDouble();

        System.out.print("Enter wall height (feet): ");
        height = sc.nextDouble();

        System.out.print("Enter number of coats: ");
        coats = sc.nextInt();
    }

    @Override
    public double calculateMaterialNeeded() {
        double area = width * height;
        double totalArea = area * coats;
        return totalArea / COVERAGE;
    }
}

ConcreteSlabProject.java
import java.util.Scanner;

public class ConcreteSlabProject extends MaterialProject {

    private double length;
    private double width;
    private double thicknessInches;

    public ConcreteSlabProject() {
        super("Concrete Slab", "cubic yards", 150.0);
    }

    @Override
    public void collectInput(Scanner sc) {

        System.out.print("Enter slab length (feet): ");
        length = sc.nextDouble();

        System.out.print("Enter slab width (feet): ");
        width = sc.nextDouble();

        System.out.print("Enter slab thickness (inches): ");
        thicknessInches = sc.nextDouble();
    }

    @Override
    public double calculateMaterialNeeded() {

        double thicknessFeet = thicknessInches / 12.0;
        double cubicFeet = length * width * thicknessFeet;
        return cubicFeet / 27.0; // convert to cubic yards
    }
}

解决方案

文件名必须以 小写字母 .java。

你把文件命名为 MaterialsCalculatorApp.Java——那个大写的J 是问题所在。

将文件改名为一个完全不同的名字，然后再改成 MaterialsCalculatorApp.java。不要一次性就改成目标名字——那样通常行不通；大多数文件系统对大小写不敏感，直接这样改不会有什么效果。

接着你还会遇到其他错误，但Stack Overflow的设计是一次只回答一个问题。