使用以下代码实现从键盘上接收一个选手的学号 给他加分 package t8; import java.util.ArrayList; import java.util.Iterator; import t5.Player; public class ArrayListDemo { public static void main(String[] args) { ArrayList<Player> players = new ArrayList<Player>(); players.add(new Player("曾佳欣", "信息与通信", "22-1", "111")); players.add(new Player("罗曼君", "信息与通信", "22-1", "222")); players.add(new Player("张嘉颖", "信息与通信", "22-1", "333")); players.add(new Player("吴少景", "信息与通信", "22-1", "444")); System.out.println("联系方式\t姓名\t班级\t系部\t得分"); for (Player player : players) { System.out.println(player.getContact() + "\t" + player.getName() + "\t" + player.getCls() + "\t" + player.getAcademy() + "\t" + player.getScore()); } } }

可以使用如下代码实现从键盘上接收一个选手的学号，并给他加分：

import java.util.ArrayList;
import java.util.Iterator;
import java.util.Scanner;
import t5.Player;

public class ArrayListDemo {

    public static void main(String[] args) {
        ArrayList<Player> players = new ArrayList<Player>();
        players.add(new Player("曾佳欣", "信息与通信", "22-1", "111"));
        players.add(new Player("罗曼君", "信息与通信", "22-1", "222"));
        players.add(new Player("张嘉颖", "信息与通信", "22-1", "333"));
        players.add(new Player("吴少景", "信息与通信", "22-1", "444"));
        
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入要加分的选手的学号：");
        String id = scanner.next();
        System.out.print("请输入要加的分数：");
        int score = scanner.nextInt();
        
        Iterator<Player> iter = players.iterator();
        while (iter.hasNext()) {
            Player player = iter.next();
            if (player.getId().equals(id)) {
                player.setScore(player.getScore() + score);
                break;
            }
        }
        
        System.out.println("联系方式\t姓名\t班级\t系部\t得分");
        for (Player player : players) {
            System.out.println(player.getContact() + "\t" + player.getName() + "\t" + 
                    player.getCls() + "\t" + player.getAcademy() + "\t" + player.getScore());
        }
        
        scanner.close();
    }

}

首先，我们引入`java.util.Scanner`类，用于从键盘上读取输入。然后，通过`Scanner`类的`next()`方法和`nextInt()`方法分别读取输入的选手学号和要加的分数。接着，我们通过`Iterator`迭代器遍历`ArrayList`中的每个选手，如果找到了指定学号的选手，则给他加分，并退出循环。最后，我们再次使用`for-each`循环输出所有选手的信息。需要注意的是，最后需要调用`Scanner`类的`close()`方法关闭输入流。