java - 对存储的数组中的特定值进行排序和显示

Question

对于我的作业，我应该制定一个程序来帮助决定棒球运动员的选秀。该程序提示球探输入有关球员的信息，并将其存储在数组中。然后，它会检查数组并显示 25 岁以下且击球率为 0.280 或以上的球员列表。该列表必须按年龄排序。

哦，菜单是必需的。

我的问题是除了标题之外它没有给我任何输出!不是排序吗？ if 语句不起作用吗？怎么了!？

players 类如下所示:

public class players 
{
    String name;
    String position;
    int age;
    double average;
}

这是我的代码:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class BlueJays 
{    
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));  
    static players[] arr;

public static void main(String[] args) throws IOException 
{
    String quit = "n";
    while("n".equals(quit))
    {
        //display menu
        System.out.println("Toronto Blue Jays Drafting Program - Main Menu");
        System.out.println("1) Input Blue Jays data");
        System.out.println("2) Display possible draft choices");      
        System.out.println("3) Quit program");
        System.out.print("Please choose an option by inputting the number of your choice: ");
        String choiceString = br.readLine();
        int choice = Integer.parseInt(choiceString);

        if(choice == 1)
        {
            inputInfo();
        }else if(choice == 2)
        {
            sortInfo();
        }else if(choice == 3)
        {
            System.out.println("Are you sure you want to quit? (y/n) ");  
            quit = br.readLine();
        }else
        {
            System.out.println("Not a valid option.");
        }                  
    }
}

//method to input names of Blue Jays
public static void inputInfo() throws IOException
{  
    players temp = new players();
    System.out.print("How many players would you like to enter? ");
    int x = Integer.valueOf(br.readLine()).intValue();
    arr = new players[x];     

    //loop through players
    for(int i = 0; i < arr.length; i++)
    {

        System.out.println("Enter player information.");

        System.out.println("Input first and last name: ");
        String name = br.readLine();
        temp.name = name;       

        System.out.println("Input position: ");
        String position = br.readLine();
        temp.position = position;

        System.out.println("Input batting average (e.g. .246): ");
        String averageString = br.readLine();
        temp.average = Double.parseDouble(averageString);

        System.out.println("Input age: ");
        temp.age = Integer.parseInt(br.readLine());
        System.out.println(" ");

        // Copy the software name and quantity to the global variables
        arr[i] = temp;
    }   
}

//method to sort and display info
public static void sortInfo()
{              
    //sort by quantity
    for(int i = 0; i < arr.length; i++)
    {
        for(int j = i+1; j < arr.length; j++)
        {
            if(arr[i].age > arr[j].age)
            {
                players  temp = arr[j];
                arr[j] = arr[i];
                arr[i] = temp;
            }
        }

    }            
    System.out.println("Draft Choices 2013");        
    //output
    for(int i = 0; i < arr.length; i++)
    {
        if (arr[i].age <= 25 && arr[i].average >= 0.280)
        {
            System.out.println("Name: " + arr[i].name);    
            System.out.println("Age: " + arr[i].age);
            System.out.println("Position: " + arr[i].position);
            System.out.println("Batting average: " + arr[i].average);
            System.out.println("   ");        
        }            

    }
    }
}

我需要很快将其交给您，因此我们将不胜感激!提前致谢!

Answer 1

代码中的 WTF 可能会导致您出现问题:

players temp = new players();
System.out.print("How many players would you like to enter? ");
int x = Integer.valueOf(br.readLine()).intValue();
arr = new players[x];     

//loop through players
for(int i = 0; i < arr.length; i++)
{

    System.out.println("Enter player information.");

    System.out.println("Input first and last name: ");
    String name = br.readLine();
    temp.name = name;       
     ....

}

您仅创建一个 players 实例并重用它。因此，您没有一个包含(例如)20 个不同玩家的数组，而是一个指向同一对象(实例)20 次的数组。该实例数据将不断被覆盖，并且仅保存您输入的最后一个玩家的数据，并且如果它的年龄> 25，由于您的过滤器，不会打印任何记录。

将实例创建移至 for 内

System.out.print("How many players would you like to enter? ");
int x = Integer.valueOf(br.readLine()).intValue();
arr = new players[x];     

//loop through players
for(int i = 0; i < arr.length; i++)
{
    players temp = new players();  // <---- THIS

    System.out.println("Enter player information.");

    System.out.println("Input first and last name: ");
    String name = br.readLine();
    temp.name = name;       
     ....

}