java - 如何标记重复的元素？

Question

我有一个名单，需要转换为所有具有相同姓氏的人都被标记的结果。例如:

来源列表:

JayReese
ClaraSmith
JohnSmith

输出:

JayReese
ClaraSmith1
JohnSmith2

Person类的代码写在下面，如何比较所有lastName，并且当有重复的lastName时，为每个添加唯一索引？应该添加什么方法？

我非常感谢任何意见和/或帮助。非常感谢。

import java.util.*;

public class Person implements Comparable<Person> {

    private String firstName;
    private String lastName;

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

    public String toString() {
        return lastName + firstName;
    }
}

Answer 1

首先，编辑 Person类或创建一个具有可设置索引字段的新类。对于您的用例来说，可比性是完全没有必要的。

public class Person {

    private String firstName;
    private String lastName;

    public int index;

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

    public String toString() {
        return lastName + firstName + (index != 0 ? index : "");
    }
}

您可以使用 HashMap<String, Integer>将编号添加到姓氏中，如下所示:

public static void numberDuplicateLastNames(List<Person> people) {
    HashMap<String, Integer> duplicatedLastNames = new HashMap<>();
    for(Person p : people) {
        if(! duplicatedLastNames.containsKey(p.lastName)) {
            duplicatedLastNames.put(p.lastName, 1);
            p.index = 1;
        } else {
            int i = duplicatedLastNames.get(p.lastName) + 1;
            duplicatedLastNames.put(p.lastName, i);
            p.index = i;
        }
    }

    //Remove index from the people who don't have a duplicate last name
    for(Person p : people) {
        if (duplicatedLastNames.get(p.lastName) == 1) {
            p.index = 0;
        }
    }
}