java - 程序每次运行时都会将 header 添加到 CSV 文件中

Question

我一年多前为 Java 编程类(class)编写了这段代码。它是一个基本的食物日志控制台应用程序，可创建 CSV 文件，并可在创建后附加用户的输入。我遇到了一个我永远无法解决的问题。我已经有一段时间没有做过太多编程了，但我对解决方案很好奇。问题是，每次程序运行时，它都会在 CSV 中插入另一个 header 。我只希望它在初始创建时插入，如果文件已经存在，则跳过。

我最初的想法是 else if (file.exists() == true) { 剩余代码块 };在“try” block 中，但它根本不写标题。

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class FoodLogWriter {

private static final String COMMA_DELIMITER = ",";
private static final String NEW_LINE_SEPARATOR = "\n";
private static final String FILE_HEADER = "Date,Food Time,Food Item,Calories,Carbohydrates,Sugar,Protein,Fiber,Total Fat";
private static Scanner kb;

public static void writeFoodLog(String fileName, File file) throws IOException {

    List<FoodLog> list = new ArrayList<FoodLog>();
    FoodLogApp app = new FoodLogApp();

    kb = new Scanner(System.in);
    String Dinput;
    String FTinput;
    String FIinput;
    double CALinput;
    double CARBinput;
    double Sinput;
    double Pinput;
    double TFinput;
    double Finput;

    int i = 0;

    while (i < 1000) {

        System.out.print("Enter the date: ");
        Dinput = kb.next();

        System.out.print("Enter the food time: ");
        FTinput = kb.next();

        System.out.print("Enter the food item: ");
        FIinput = kb.next();

        System.out.print("Enter the calories: ");
        CALinput = kb.nextDouble();

        System.out.print("Enter the carbohydrates: ");
        CARBinput = kb.nextDouble();

        System.out.print("Enter the sugar: ");
        Sinput = kb.nextDouble();

        System.out.print("Enter the protein: ");
        Pinput = kb.nextDouble();

        System.out.print("Enter the fiber: ");
        Finput = kb.nextDouble();

        System.out.print("Enter the total fat: ");
        TFinput = kb.nextDouble();

        list.add(app.createFoodLog(Dinput, FTinput, FIinput, CALinput, CARBinput, Sinput, Pinput, Finput, TFinput));

        System.out.println("");
        System.out.print("Do you have another item to input? ");
        String response = kb.next();
        System.out.println("");

        if (response.equalsIgnoreCase("no")) {

            app.printFoodLog(list);
            break;

        } else {
            i++;
        }

        kb.nextLine();

    }

    FileWriter fileWriter = null;

    try {

        fileWriter = new FileWriter(fileName, true);

        if (file.exists() == false) {
            fileWriter.write(FILE_HEADER.toString());
        }
        fileWriter.append(NEW_LINE_SEPARATOR);

        for (FoodLog FL : list) {
            fileWriter.append(String.valueOf(FL.getDate()));
            fileWriter.append(COMMA_DELIMITER);
            fileWriter.append(String.valueOf(FL.getFoodTime()));
            fileWriter.append(COMMA_DELIMITER);
            fileWriter.append(String.valueOf(FL.getFoodItem()));
            fileWriter.append(COMMA_DELIMITER);
            fileWriter.append(String.valueOf(FL.getCalories()));
            fileWriter.append(COMMA_DELIMITER);
            fileWriter.append(String.valueOf(FL.getCarbohydrates()));
            fileWriter.append(COMMA_DELIMITER);
            fileWriter.append(String.valueOf(FL.getSugar()));
            fileWriter.append(COMMA_DELIMITER);
            fileWriter.append(String.valueOf(FL.getProtein()));
            fileWriter.append(COMMA_DELIMITER);
            fileWriter.append(String.valueOf(FL.getFiber()));
            fileWriter.append(COMMA_DELIMITER);
            fileWriter.append(String.valueOf(FL.getTotalFat()));
            fileWriter.append(NEW_LINE_SEPARATOR);
        }

        System.out.println("CSV file was created successfully.");

    } catch (Exception e) {
        System.out.println("Error in FoodLogWriter.");
        e.printStackTrace();
    } finally {

        try {
            fileWriter.flush();
            fileWriter.close();
        } catch (IOException e) {
            System.out.println("Error while flushing/closing file writer.");
            e.printStackTrace();
        }
    }

}

}

Answer 1

以下是剩余的类(class):

public class FoodLog {

private String Date;
private String FoodTime;
private String FoodItem;
private double Calories;
private double Carbohydrates;
private double Sugar;
private double Fiber;
private double Protein;
private double TotalFat;

public FoodLog(String Date, String FoodTime, String FoodItem, double Calories, double Carbohydrates, double Sugar,
        double Fiber, double Protein, double TotalFat) {

    // super();
    this.Date = Date;
    this.FoodTime = FoodTime;
    this.FoodItem = FoodItem;
    this.Calories = Calories;
    this.Carbohydrates = Carbohydrates;
    this.Sugar = Sugar;
    this.Fiber = Fiber;
    this.Protein = Protein;
    this.TotalFat = TotalFat;

}

public String getDate() {
    return Date;
}

public void setDate(String date) {
    Date = date;
}

public String getFoodTime() {
    return FoodTime;
}

public void setFoodTime(String foodTime) {
    FoodTime = foodTime;
}

public String getFoodItem() {
    return FoodItem;
}

public void setFoodItem(String foodItem) {
    FoodItem = foodItem;
}

public double getCalories() {
    return Calories;
}

public void setCalories(double calories) {
    Calories = calories;
}

public double getCarbohydrates() {
    return Carbohydrates;
}

public void setCarbohydrates(double carbohydrates) {
    Carbohydrates = carbohydrates;
}

public double getSugar() {
    return Sugar;
}

public void setSugar(double sugar) {
    Sugar = sugar;
}

public double getFiber() {
    return Fiber;
}

public void setFiber(double fiber) {
    Fiber = fiber;
}

public double getProtein() {
    return Protein;
}

public void setProtein(double protein) {
    Protein = protein;
}

public double getTotalFat() {
    return TotalFat;
}

public void setTotalFat(double totalFat) {
    TotalFat = totalFat;
}

public String toString() {
    return "FoodLog [Date = " + Date + ", Food Time = " + FoodTime + ", Food Item = " + FoodItem + ", Calories = "
            + Calories + ", Carbohydrates = " + Carbohydrates + ", Sugar = " + Sugar + ", Fiber = " + Fiber
            + ", Protein = " + Protein + ", Total Fat = " + TotalFat + "]";

}

}

import java.io.File;
import java.io.IOException;
import java.util.List;

public class FoodLogApp {

public static void main(String[] args) throws IOException {

    File file = new File("FoodLog.csv");
    String fileName = System.getProperty("user.home") + "/FoodLog.csv";
    FoodLogWriter.writeFoodLog(fileName, file);

}

public FoodLog createFoodLog(String Date, String FoodTime, String FoodItem, double Calories, double Carbohydrates,
        double Sugar, double Fiber, double Protein, double TotalFat) {

    return new FoodLog(Date, FoodTime, FoodItem, Calories, Carbohydrates, Sugar, Fiber, Protein, TotalFat);
}

public void printFoodLog(List<FoodLog> list) {

    for (FoodLog FL : list) {

        System.out.println("===========================================");
        System.out.println("Food Time : " + FL.getFoodTime());
        System.out.println("Food Item : " + FL.getFoodItem());
        System.out.println("Calories : " + FL.getCalories());
        System.out.println("Carbohydrates : " + FL.getCarbohydrates());
        System.out.println("Sugar : " + FL.getSugar());
        System.out.println("Protein : " + FL.getProtein());
        System.out.println("Fiber : " + FL.getFiber());
        System.out.println("Total Fat : " + FL.getTotalFat());
        System.out.println("===========================================");
        System.out.println("");         
    }

}

}