比较 ArrayList 中的两个字符串，找出每个人的最高成绩

Question

我正在尝试在这里实现一个 ArrayList，每个人都有最高分。我需要阅读文本文件并从那里整理出包含人名和年级的行。

排序后 namesWithGrades 输出如下所示：

[David Doe 3, Carol White 3, Bob Brown 4, Bob Brown 4, Alice Smith 4, David Doe 4, Alice Smith 5, Bob Brown 5]

所需的输出应按任何顺序显示如下：

[Carol White 3, David Doe 4, Alice Smith 5, Bob Brown 5]

我的问题是，我如何能够比较 namesWithGrade ArrayList 中的姓名和成绩以获得 result ArrayList 所需的结果？

到目前为止我的主要代码：

public List<String> getFullNamesWithHighestGrade() {
        readLines();
        List<String> namesWithGrade = new ArrayList<>();
        List<String> result = new ArrayList<>();
        for(String person: dataOrig){
            String[] data = person.split("\|");
            namesWithGrade.add(data[0] + " " + data[1] + " " + data[3]);
        }
        namesWithGrade.sort(Comparator.comparing(s -> s.split(" ")[2]));
        System.out.println(namesWithGrade);
        
        return result;
    }

正在从 grades.txt 文件读取数据：

private static final String FILE_PATH = "src/ex1/grades.txt";
    public List<String> dataOrig;

    private List<String> readLines() {
        try {
            dataOrig = Files.readAllLines(Paths.get(FILE_PATH));
            return dataOrig;
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

grades.txt 文件:

Alice|Smith|math|5
Bob|Brown|english|4
David|Doe|math|3
Bob|Brown|math|4
Bob|Brown|chemistry|5
Alice|Smith|english|4
Carol|White|chemistry|3
David|Doe|chemistry|4

Answer 1

创建一个 HashMap。这是一个可能的例子：

HashMap<String, Integer> results = new HashMap<String, Integer>();

for(String person: dataOrig) {
    String[] data = person.split(“\|”);
    String currentName = data[0] + “ “ + data[1]; //get the name of the current line
    int currentGrade = Integer.parseInt(data[3]); //get the grade of the current line 
    if(results.containsKey(currentName)) { //if the name is in the HashMap with a grade
        if(currentGrade > results.get(currentName)) { //if the current grade is greater than the one that is already in the HashMap, replace it.
            results.put(currentName, currentGrade);
        }
    }
    else //if the name hasn’t been added to the HashMap yet, put it in.
        results.put(currentName, currentGrade);
}

HashMap 现在应该包含具有正确最高等级的名称。无需使用 2 个 ArrayList。您可以使用此循环打印出结果。要按值对 HashMap 进行排序，请查看此 link：https://www.google.com/amp/s/www.geeksforgeeks.org/sorting-a-hashmap-according-to-values/amp/

for(Map.Entry<String, Integer> entry : results.entrySet()) {
    System.out.println(entry.getKey() + “ “ + entry.getValue());
}

比较 ArrayList 中的两个字符串，找出每个人的最高成绩

Compare two strings in ArrayList to find each person highest grade

java

sorting

arraylist

txt