Java：当用户给出的名字按字母顺序排列时，只打印第一个和最后一个

Question

import java.util.Scanner;
import java.util.Arrays;
import java.util.*; 
import java.util.TreeSet; 

public class personSorter 
{
  public static void main(String[] args)
  {
  int count = 0; 
  Scanner in = new Scanner(System.in);

  boolean more = true;
  Person first = null;
  Person last = null; 

  Person[] people= new Person[10]; //my array 

  while(more)
  {
  System.out.println("Please enter the person's name or a blank line to quit");
  String names = in.nextLine(); 

  if (names.equals(""))
     {    
     more = false;
     }
 else
 {
        Person p1 = new Person(names);  //creating 10 person objects to be used
        Person p2 = new Person(names);
        Person p3 = new Person(names);
        Person p4 = new Person(names);
        Person p5 = new Person(names);
        Person p6 = new Person(names);
        Person p7 = new Person(names);
        Person p8 = new Person(names);
        Person p9 = new Person(names);
        Person p10 = new Person(names); 

       people[count] = p1; // using my person objects and declaring the index of variable count
       people[count] = p2;
       people[count] = p3;
       people[count] = p4;
       people[count] = p5;
       people[count] = p6;
       people[count] = p7;
       people[count] = p8;
       people[count] = p9;
       people[count] = p10;

        first = people[count];
        last  = people[count];

    TreeSet<String> treeSet = new TreeSet<String>(); //using TreeSort to get the names entered by user in ascending order

     treeSet.add(names);
     treeSet.add(names);
     treeSet.add(names);
     treeSet.add(names);
     treeSet.add(names);
     treeSet.add(names);
     treeSet.add(names);
     treeSet.add(names);
     treeSet.add(names);
     treeSet.add(names);



   first.compareTo(p1); //after TreeSort first compare method called of first object as it is now the first name in alphabet order
   last.compareTo(p10); //after TreeSort last compare method called of last object as it is now the last name in alphabet order

  count++;       
  }
}

//printing out the first and last name(in alphabet order) of the entered names 
  System.out.println("First: " + first.toString()); 
  System.out.println("Last: " + last.toString());
 } 
 }

public class Person implements Comparable <Person> 
    {
        private String name;

public Person(String n) 
{
    name = n;
}

public String getName() 
{
    return name;
}

   @Override
public int compareTo(Person others) 
{
    if (name.compareTo(others.name) == 1) 
    {
        return 0;
    } 
    else if (name.compareTo(others.name) < 0) 
    {
        return -1;
    } 
    else 
    {
        return 1;
    }
   }
   public String toString() 
   {
   return "[" + name + "]";
   }

}

Answer 1

下面是您的代码的简化和正确工作的版本（如果我很好地理解主方法的目标的话）：

public static void main(String[] args) {
    int count = 0;
    Scanner in = new Scanner(System.in);

    boolean more = true;
    int MAX_SIZE = 10;

    Person[] people = new Person[MAX_SIZE]; // my array

    while (more && count < MAX_SIZE) {
        System.out.println("Please enter the person's name or a blank line to quit");
        String name = in.nextLine();

        if (name.equals("")) {
            more = false;
        } else {
            Person p = new Person(name); 
            people[count++] = p;
        }
    }
    in.close();

    Arrays.sort(people, 0, count);

    // printing out the first and last name(in alphabet order) of the entered names
    System.out.println("First: " + people[0]);
    System.out.println("Last: " + people[count - 1]);
}

几点考虑：

• 不需要TreeSort对数组进行排序，只需使用arrays.sort方法即可。还要注意它作为输入的其他参数，以将其限制为开始和结束，这些参数不一定与数组的完整初始大小匹配（因为您是从控制台输入填充数组的）
• 要填充数组的不同元素，需要移动到它的下一个索引，因此每次迭代时count变量都需要增加一个
• 数组排序后，第一个和最后一个元素不需要临时变量，只需使用第一个索引（0）和最后一个填充(count-1)
• 还需要将整个循环限制为数组的最大大小，以避免其大小变大并出现异常

希望您能更好地理解循环、数组、排序以及如何改进代码。

public static void main(String[] args) {
    int count = 0;
    Scanner in = new Scanner(System.in);
    int MAX_SIZE = 10;
    Person[] people = new Person[MAX_SIZE];

    System.out.println("Please enter the person's name or a blank line to quit");
    String line = in.nextLine();

    String[] names = line.split(" ");
    for (int i = 0; i < MAX_SIZE; i++) {
        Person p = new Person(names[i]);
        people[count++] = p;
    }
    in.close();

    Arrays.sort(people, 0, count);

    // printing out the first and last name(in alphabet order) of the entered names
    System.out.println("First: " + people[0]);
    System.out.println("Last: " + people[count - 1]);
}