我无法弄清楚为啥我的数组列表没有使用我所说的新值进行更新

Posted 2023-04-17

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【中文标题】我无法弄清楚为啥我的数组列表没有使用我所说的新值进行更新【英文标题】：I cannot figure out why my Array list is not updating with the new values that I am stating我无法弄清楚为什么我的数组列表没有使用我所说的新值进行更新 【发布时间】：2019-06-02 17:36:25 【问题描述】：

如果我在问这个问题时犯了任何错误，请告诉我我知道这是一个专业论坛，这是我的第一篇文章。因此，我正在尝试为我的 APCS 高中课程编写代码，但是遇到了问题。仅供参考，这里是我遇到问题的部分代码的说明 -

3.) 创建一个名为 updateLocation 的方法，将国家/地区添加到运行的城市（例如，英国伦敦）。打印列表。

我遇到的问题发生在第 3 步。我已经编写了 updateLocation 方法，并为该方法编写了 if 循环，以用 Country 替换已定义的位置，但是，它没有正确输出。

这是我的代码-

import java.util.ArrayList;


public class Runner 
    private double time;
    private String atheleteName;
    private String nationality;
    private String date;
    private String location;

    public Runner(double time, String atheleteName, String nationality, String date, String location) 
        this.time = time;
        this.atheleteName = atheleteName;
        this.nationality = nationality;
        this.date = date;
        this.location = location;
    

    public double getTime() 
        return time;
    

    public String getAtheleteName() 
        return atheleteName;
    

    public String getNationality() 
        return nationality;
    

    public String getDate() 
        return date;
    

    public String getLocation() 
        return location;
    

    public void setTime(double time) 
        this.time = time;
    

    public void setAtheleteName(String atheleteName) 
        this.atheleteName = atheleteName;
    

    public void setNationality(String nationality) 
        this.nationality = nationality;
    

    public void setDate(String date) 
        this.date = date;
    

    public void setLocation(String location) 
        this.location = location;
    

    public String toString() 
        return  
        time + atheleteName + nationality + date + location;

    

    public static void main(String[] args) 

        ArrayList<Runner> runners = new ArrayList<>();

        runners.add(new Runner(     9.58,"         Usain Bolt   ","     Jamaica   ","   16 August 2009   ","      Berlin   "));
        runners.add(new Runner(     9.69,"         Tyson Gray   ","     USA   ","       20 September 2009   ","   Shanghai   "));
        runners.add(new Runner(     9.69,"         Yohan Blake   ","    Jamaica   ","   23 August 2012   ","      Lausanne"));
        runners.add(new Runner(     9.72,"         Asafa Powell   ","   Jamaica   ","   02 September 2008   ","   Lausanne   "));
        runners.add(new Runner(     9.78,"         Nesta Carter   ","   Jamaica   ","   29 August 2010   ","      Rieti   "));
        runners.add(new Runner(     9.79,"         Maurice Greene   "," USA   ","       16 June 1999   ","        Athens   "));
        runners.add(new Runner(     9.79,"         Justin Gatlin   ","  USA   ","       05 August 2012   ","      London   "));
        runners.add(new Runner(     9.80,"          Steve Mullings   "," Jamaica   ","   04 June 2011   ","        Eugene   "));
        runners.add(new Runner( 9.84,"         Donovan Bailey   "," Canada   ","    27 July 1996   ","        Atlanta   "));
        runners.add(new Runner(9.84,"         Bruny Surin   ","    Canada   ","    22 August 1999   ","      Seville   "));
        System.out.println("\nOriginal Array- ");
        System.out.println("");
        System.out.println("Time(sec):      Name:        Nationality:      Date:              Location:");
        System.out.println("---------------------------------------------------------------------------");
        printRunners(runners);
        updateLocation(runners);
        System.out.println("\nUpdate Runners- ");
        System.out.println("");
        System.out.println("Time(sec):      Name:        Nationality:      Date:              Location:");
        System.out.println("---------------------------------------------------------------------------");
        printRunners(runners);
        insertName(runners,10.49,"   Florence (G.) Joyner   ","USA   ","       06 July 1988   ","        Indianapolis, Indiana   ");
        System.out.println("\nUpdate Runners- ");
        System.out.println("");
        System.out.println("Time(sec):      Name:        Nationality:      Date:              Location:");
        System.out.println("---------------------------------------------------------------------------");
        printRunners(runners);
        replaceName(runners,"         Bruny Surin   ","         Carl Lewis   ",   9.86   ,"     USA   ","       23 August 1991   ","      Tokyo, Japan   ");
        System.out.println("\nUpdate Runners- ");
        System.out.println("");
        System.out.println("Time(sec):      Name:        Nationality:      Date:              Location:");
        System.out.println("---------------------------------------------------------------------------");
        printRunners(runners);

    

    public static void printRunners(ArrayList<Runner> runners)
        for(Runner runner:runners)
            System.out.println(runner);
     

    public static void updateLocation(ArrayList<Runner> runners)
        for(Runner runner : runners)
            if(runner.getLocation().equalsIgnoreCase("Berlin"))
                runner.setLocation("Berlin, Germany");
            else if(runner.getLocation().equalsIgnoreCase("Shanghai"))
                runner.setLocation("Shanghai, China");
            else if(runner.getLocation().equalsIgnoreCase("London"))
                runner.setLocation("London, England");
            else if(runner.getLocation().equalsIgnoreCase("Athens"))
                runner.setLocation("Athens, Greece");
             else if(runner.getLocation().equalsIgnoreCase("Eugene"))
                runner.setLocation("Eugene, South Africa");
             else if(runner.getLocation().equalsIgnoreCase("Seville"))
                runner.setLocation("Seville, France");
            else if(runner.getLocation().equalsIgnoreCase("Lausanne"))
                runner.setLocation("Lausanne, Spain");
            else if(runner.getLocation().equalsIgnoreCase("Rieti"))
                runner.setLocation("Rieti, Australia");
            else if(runner.getLocation().equalsIgnoreCase("Atlanta"))
                runner.setLocation("Atlanta, USA");
            
        
    

    public static void insertName(ArrayList<Runner> runners, double time, String atheleteName, String nationality, String date, String location)
        Runner runner = new Runner(time,atheleteName,nationality,date,location);
        runners.add(runner);
    

    public static void replaceName(ArrayList<Runner> runners, String searchName, String replaceName, double time, String nationality, String date, String location)
        for(Runner runner: runners)
            if(runner.getAtheleteName().equalsIgnoreCase(searchName))
                runner.setTime(time);
                runner.setAtheleteName(replaceName);
                runner.setNationality(nationality);
                runner.setDate(date);
                runner.setLocation(location);

我希望我的结果是-

时间（秒）：姓名：国籍：日期：地点：

9.58 Usain Bolt 牙买加 2009 年 8 月 16 日，德国柏林

9.69 Tyson Gray 美国 2009 年 9 月 20 日中国上海

9.69 Yohan Blake 牙买加 2012 年 8 月 23 日，西班牙洛桑

9.72 Asafa Powell Jamaica 2008 年 9 月 2 日，西班牙洛桑

9.78 牙买加内斯塔卡特 2010 年 8 月 29 日澳大利亚

9.79 Maurice Greene 美国 1999 年 6 月 16 日，希腊雅典

9.79 Justin Gatlin 美国 2012 年 8 月 5 日，英国伦敦

9.8 Steve Mullings 牙买加 2011 年 6 月 4 日南非尤金

9.84 Donovan Bailey 加拿大 1996 年 7 月 27 日，美国亚特兰大

9.84 Bruny Surin 加拿大 1999 年 8 月 22 日法国塞维利亚 ..................................................... ………………………………………………………………………………………………………… 但是，我的输出看起来像这样-

时间（秒）：姓名：国籍：日期：地点：

9.58 Usain Bolt 牙买加 2009 年 8 月 16 日柏林

9.69 Tyson Gray 美国 2009 年 9 月 20 日上海

9.69 Yohan Blake 牙买加 2012 年 8 月 23 日洛桑

9.72 Asafa Powell 牙买加 2008 年 9 月 2 日洛桑

9.78 内斯塔·卡特牙买加 2010 年 8 月 29 日列蒂

9.79 Maurice Greene 美国 1999 年 6 月 16 日雅典

9.79 Justin Gatlin 美国 2012 年 8 月 5 日伦敦

9.8 Steve Mullings 牙买加 2011 年 6 月 4 日尤金

9.84 Donovan Bailey 加拿大 1996 年 7 月 27 日亚特兰大

9.84 布鲁尼苏林加拿大 1999 年 8 月 22 日塞维利亚

如果您对代码有任何疑问，请告诉我。

【问题讨论】：

您在updateLocation 方法中的所有if 检查都失败了，因为它们都用空格填充。如果您绝对需要填充空格，您可以在 updateLocation 方法中使用 runner.getLocation().trim()。 【参考方案1】：

字符串" Berlin " 和"Berlin" 不相等（即使您忽略大小写比较它们。第一个包含前导和尾随空格。删除它们或将runner.getLocation() 替换为runner.getLocation().trim()。

【讨论】：

【参考方案2】：

将updateLocation 方法更新为：

public static void updateLocation(ArrayList<Runner> runners)
    for(Runner runner : runners)
        if(runner.getLocation().trim().equalsIgnoreCase("Berlin"))
            runner.setLocation("Berlin, Germany");
        else if(runner.getLocation().trim().equalsIgnoreCase("Shanghai"))
            runner.setLocation("Shanghai, China");
        else if(runner.getLocation().trim().equalsIgnoreCase("London"))
            runner.setLocation("London, England");
        else if(runner.getLocation().trim().equalsIgnoreCase("Athens"))
            runner.setLocation("Athens, Greece");
         else if(runner.getLocation().trim().equalsIgnoreCase("Eugene"))
            runner.setLocation("Eugene, South Africa");
         else if(runner.getLocation().trim().equalsIgnoreCase("Seville"))
            runner.setLocation("Seville, France");
        else if(runner.getLocation().trim().equalsIgnoreCase("Lausanne"))
            runner.setLocation("Lausanne, Spain");
        else if(runner.getLocation().trim().equalsIgnoreCase("Rieti"))
            runner.setLocation("Rieti, Australia");
        else if(runner.getLocation().trim().equalsIgnoreCase("Atlanta"))
            runner.setLocation("Atlanta, USA");

搜索字符串包含空格，而 expected string 不包含空格

【讨论】：

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