java如何对名称的字符串列表使用二级字母排序？

Question

我正在尝试一种方法，当给定一个名为名字和姓氏的字符串时，名字被;分割，名字被:->

"Fred:Corwill;Wilfred:Corwill;Barney:Tornbull;Betty:Tornbull;Bjon:Tornbull;Raphael:Corwill;Alfred:Corwill"

我想返回一个字符串，它将所有名字按大写字母排序，并根据姓氏和共享相同姓氏的人按字母顺序排序，然后在共享相同姓氏的人的名字之间再次排序（二级排序）。（我还特意将所有内容改为大写）

并返回排序名称的字符串，因此对于上面的示例，它应该返回：

"(CORWILL, ALFRED)(CORWILL, FRED)(CORWILL, RAPHAEL)(CORWILL, WILFRED)(TORNBULL, BARNEY)(TORNBULL, BETTY)(TORNBULL, BJON)"

它根据姓氏的字母顺序进行排序，然后在拥有相同姓氏的人之间进行排序，第二类是名字

我设法进行了主要排序，即按字母顺序对姓氏进行排序，但我不确定如何进行第二次排序（在共享相同姓氏的人之间）。我曾想拆分成子数组或类似的东西，但我不知道如何做到这一点

解决这个问题的办法是什么

以下是我迄今为止管理的内容（主要排序工作）：

public class Solution {
    public static String meeting(String s) {
        String m = "";
        List<String> name = new ArrayList<String>();
        for (String i : s.toUpperCase().split(";")) {
            String[] n = i.split(":");
            name.add(n[0] + " " + n[1]);
        }
        //main sorting
        java.util.Collections.sort(name);
        //secondary sorting and go through each different last name
        for (String i : name) {
            String[] n = i.split(" ");
            String lastname = n[1];
            // new list for the ppl who share same last name
            List<String> samel = new ArrayList<String>();
            samel.add(n[0]);
            for (String ss : name) {
                String[] nn = ss.split(" ");
                if (nn[1] == lastname) {
                    samel.add(nn[0]);
                }
            }
            //sort the ppl alphabetically with the same last name
            java.util.Collections.sort(samel);
        }
        for (String i : name) {
            String[] n = i.split(" ");
            m += ("(" + n[0] + " , " + n[1] + ")");
        }
        return m;
    }
}

我尝试进行二次排序，但未成功

如果我不够清楚的话，有两种排序方式，一种是按姓氏字母顺序进行的主排序，另一种是只对姓氏完全相同的人进行的次排序，然后根据字母顺序对他们的名字进行相应的排序。因此，如果我们有两个人叫matt cohn和mill cohn，那么他们的姓氏和姓氏中的第一个字母相同，但是a在o之前，所以输出应该是(COHN , MATT)(COHN, MILL)，而不是相反

在下面的解决方案中，我运行了它并得到一个错误：

input String:
Alexis:Wahl;John:Bell;Victoria:Schwarz;Abba:Dorny;Grace:Meta;Ann:Arno;Madison:STAN;Alex:Cornwell;Lewis:Kern;Megan:Stan;Alex:Korn

Actual: (ARNO, ANN)(BELL, JOHN)(CORNWELL, ALEX)(DORNY, ABBA)(KERN, LEWIS)(KORN, ALEX)(META, GRACE)(STAN, MADISON)(SCHWARZ, VICTORIA)(STAN, MEGAN)(WAHL, ALEXIS)

Expect: (ARNO, ANN)(BELL, JOHN)(CORNWELL, ALEX)(DORNY, ABBA)(KERN, LEWIS)(KORN, ALEX)(META, GRACE)(SCHWARZ, VICTORIA)(STAN, MADISON)(STAN, MEGAN)(WAHL, ALEXIS)
false

但结果却是假的

Answer 1

如果您使用的是Java stream，那么可以像这样使用sorted：

return Arrays.stream(s.split(";"))
        .map(p -> p.split(":"))
        .sorted(Comparator.comparing((String[] p) -> p[1]).thenComparing((String[] p) -> p[0]))
        .map(p -> String.format("(%s, %s)", p[1].toUpperCase(), p[0].toUpperCase()))
        .collect(Collectors.joining());

输出

(CORWILL, ALFRED)(CORWILL, FRED)(CORWILL, RAPHAEL)(CORWILL, WILFRED)(TORNBULL, BARNEY)(TORNBULL, BETTY)(TORNBULL, BJON)

---

我还建议使用对象而不是字符串来存储信息，使用这种方法不是一种好的做法

Answer 2

您可以使用比较器链先按一个值排序，然后再按另一个值排序：

String str = "Fred:Corwill;Wilfred:Corwill;Barney:Tornbull;" +
        "Betty:Tornbull;Bjon:Tornbull;Raphael:Corwill;Alfred:Corwill";

List<Map.Entry<String, String>> list = Stream.of(str)
        .map(String::toUpperCase)
        // Stream<String>
        .flatMap(s -> Arrays.stream(s.split(";")))
        // Stream<String[]>
        .map(s -> s.split(":"))
        // Stream<Map.Entry<String,String>>
        .map(arr -> Map.entry(arr[1], arr[0]))
        // sort by last name, then by first name
        .sorted(Map.Entry.<String, String>comparingByKey()
                .thenComparing(Map.Entry::getValue))
        .collect(Collectors.toList());

// output line by line
list.forEach(System.out::println);

输出：

CORWILL=ALFRED
CORWILL=FRED
CORWILL=RAPHAEL
CORWILL=WILFRED
TORNBULL=BARNEY
TORNBULL=BETTY
TORNBULL=BJON

---

^{另见：How to sort by a field of class with its own comparator?}

Answer 3

一种可能的解决方案如下：

public class ExtractAndSortNames {

    public static String extractAndSort(String s) {
        return Stream.of(s.split(";"))
                .map(String::toUpperCase)
                .map(ExtractAndSortNames::extractPersonFirstNameAndLastName)
                .sorted(Comparator.comparing(FirstNameAndLastName::getLastName).thenComparing(FirstNameAndLastName::getFirstName))
                .map(FirstNameAndLastName::format)
                .collect(Collectors.joining());
    }

    private static FirstNameAndLastName extractPersonFirstNameAndLastName(String personName) {
        var split = personName.split(":");
        var firstName = split[0];
        var lastName = split[1];
        return new FirstNameAndLastName(firstName, lastName);
    }

    private static class FirstNameAndLastName {
        private final String firstName;
        private final String lastName;

        public FirstNameAndLastName(String firstName, String lastName) {
            this.firstName = firstName;
            this.lastName = lastName;
        }
        
        public String getFirstName() {
            return firstName;
        }
        
        public String getLastName() {
            return lastName;
        }
        
        public String format() {
            return String.format("(%s, %s)", this.lastName, this.firstName);
        }
    }
}

无流的解决方案：

public class ExtractAndSortNames {

    public static String extractAndSort(String s) {
        List<FirstNameAndLastName> toSort = new ArrayList<>();
        for (String s1 : s.split(";")) {
            String toUpperCase = s1.toUpperCase();
            FirstNameAndLastName firstNameAndLastName = extractPersonFirstNameAndLastName(toUpperCase);
            toSort.add(firstNameAndLastName);
        }
        toSort.sort(Comparator.comparing(FirstNameAndLastName::getLastName).thenComparing(FirstNameAndLastName::getFirstName));
        StringBuilder sb = new StringBuilder();
        for (FirstNameAndLastName firstNameAndLastName : toSort) {
            String format = firstNameAndLastName.format();
            sb.append(format);
        }
        return sb.toString();
    }

    private static FirstNameAndLastName extractPersonFirstNameAndLastName(String personName) {
        var split = personName.split(":");
        var firstName = split[0];
        var lastName = split[1];
        return new FirstNameAndLastName(firstName, lastName);
    }

    private static class FirstNameAndLastName {
        private final String firstName;
        private final String lastName;

        public FirstNameAndLastName(String firstName, String lastName) {
            this.firstName = firstName;
            this.lastName = lastName;
        }

        public String getFirstName() {
            return firstName;
        }

        public String getLastName() {
            return lastName;
        }

        public String format() {
            return String.format("(%s, %s)", this.lastName, this.firstName);
        }
    }
}

和测试：

class ExtractAndSortNamesTest {

    @Test
    void test() {
        var input = "Fred:Corwill;Wilfred:Corwill;Barney:Tornbull;Betty:Tornbull;Bjon:Tornbull;Raphael:Corwill;Alfred:Corwill";
        var result = ExtractAndSortNames.extractAndSort(input);

        assertEquals("(CORWILL, ALFRED)(CORWILL, FRED)(CORWILL, RAPHAEL)(CORWILL, WILFRED)(TORNBULL, BARNEY)(TORNBULL, BETTY)(TORNBULL, BJON)", result);
    }

    @Test
    void test2() {
        var input = "Alexis:Wahl;John:Bell;Victoria:Schwarz;Abba:Dorny;Grace:Meta;Ann:Arno;Madison:STAN;Alex:Cornwell;Lewis:Kern;Megan:Stan;Alex:Korn";
        var result = ExtractAndSortNames.extractAndSort(input);

        assertEquals("(ARNO, ANN)(BELL, JOHN)(CORNWELL, ALEX)(DORNY, ABBA)(KERN, LEWIS)(KORN, ALEX)(META, GRACE)(SCHWARZ, VICTORIA)(STAN, MADISON)(STAN, MEGAN)(WAHL, ALEXIS)", result);
    }
}

使用具有预览功能的Java 15进行奖励回合：

public class ExtractAndSortNames {

    public static String extractAndSort(String s) {
        return Stream.of(s.split(";"))
                .map(String::toUpperCase)
                .map(FirstNameAndLastName::from)
                .sorted(Comparator.comparing(FirstNameAndLastName::lastName).thenComparing(FirstNameAndLastName::firstName))
                .map(FirstNameAndLastName::format)
                .collect(Collectors.joining());
    }

    private static record FirstNameAndLastName (String firstName, String lastName) {
        private static FirstNameAndLastName from(String personName) {
            var split = personName.split(":");
            var firstName = split[0];
            var lastName = split[1];

            return new FirstNameAndLastName(firstName, lastName);
        }

        public String format() {
            return "(%s, %s)".formatted(this.lastName, this.firstName);
        }
    }
}