如何将多个类合并为单个Java文件？附本人编写的代码示例

Hey there! I see you're trying to keep all your rainfall statistics logic in a single Java file—great call for simplicity. Let's work through the issues in your current code and get it fully functional.

First, let's spot the problems in your existing code: #

• The totalRainfall variable in getTotalRainfall() isn't initialized, which will cause a compile error.
• getAverageRainfall() is trying to call getTotalRainfall(...) with invalid parameters, but your getTotalRainfall() method doesn't take any arguments.
• There's no way to initialize the rainfallStats array, so you'd hit a NullPointerException when trying to use it.
• No main method to run the class directly (since you want a single executable file).

Here's the corrected, complete single-file version: #

import javax.swing.JOptionPane;

public class Raindrop {
    private double[] rainfallStats;

    // Constructor to initialize the rainfall data array
    public Raindrop(double[] rainfallData) {
        this.rainfallStats = rainfallData;
    }

    public double getTotalRainfall() {
        // Initialize total to 0.0 to start valid accumulation
        double totalRainfall = 0.0;
        for (int index = 0; index < rainfallStats.length; index++) {
            totalRainfall += rainfallStats[index];
        }
        return totalRainfall;
    }

    public double getAverageRainfall() {
        // Guard against empty array to avoid division by zero
        if (rainfallStats == null || rainfallStats.length == 0) {
            return 0.0;
        }
        return getTotalRainfall() / rainfallStats.length;
    }

    // Main method to run the program directly from this single file
    public static void main(String[] args) {
        // Example: Get number of months from user
        String input = JOptionPane.showInputDialog("Enter number of months to track rainfall:");
        int numMonths = Integer.parseInt(input);
        double[] rainfallData = new double[numMonths];

        // Collect rainfall data for each month
        for (int i = 0; i < numMonths; i++) {
            String rainInput = JOptionPane.showInputDialog("Enter rainfall for month " + (i + 1) + ":");
            rainfallData[i] = Double.parseDouble(rainInput);
        }

        // Create Raindrop instance and calculate stats
        Raindrop rainTracker = new Raindrop(rainfallData);
        double total = rainTracker.getTotalRainfall();
        double average = rainTracker.getAverageRainfall();

        // Display results
        JOptionPane.showMessageDialog(null,
                "Total Rainfall: " + total + " inches\n" +
                "Average Monthly Rainfall: " + average + " inches");
    }
}

Key improvements explained: #

• Added a constructor to safely initialize the rainfallStats array with user-provided data.
• Initialized totalRainfall to 0.0 in getTotalRainfall() to ensure valid numeric accumulation.
• Fixed getAverageRainfall() to call the correct无参getTotalRainfall() method, plus added a check to avoid division by zero if the array is empty.
• Added a main method so you can compile and run this single .java file directly, using JOptionPane to interact with the user for data input and result display.

内容的提问来源于stack exchange，提问作者Junior Planell LILCORE4