对于teamSize，可以使用||（OR）运算符，用于验证是否必须再次询问该值是小于9还是大于15。因此，您可以使用以下方法添加该值：

while (teamSize < 9 || teamSize > 15) { //Change introduced here
    System.out.println("Number of players Invalid. \nHow many players do you wish per team?");
    System.out.println("(Enter a value in the range 9 - 15): ");
    teamSize = scan.nextInt();
}

对于players，验证操作是可以的，只要记住再次请求该值，否则while将进入无限循环：

while (players < 1) {
    System.out.println("Number of players Invalid. \nHow many players are available?");
    players = scan.nextInt();
}

就是这样!

我喜欢用这样的句型反复问问题并得到答案：

int teamSize;
boolean valid = false;
do {
    System.out.println("How many players do you wish per team?");
    System.out.print("(Enter a value in the range 9 - 15): ");
    teamSize = scan.nextInt();
    valid = (teamSize >= 9 && teamSize <=15);
    if (!valid) {
        System.out.println("Number of players Invalid.");
    } 
} while (!valid);

如果用户输入是无效的，则必须确保用户可以输入新值。要为teamSize或players输入新值，应在while循环中使用scan.nextInt()初始化变量，而不是之前。
注意：由于Java的变量作用域规则，变量仍然必须在while循环外声明，以确保循环后的可访问性，这一点很重要。

import java.util.Scanner;

class SoccerTeam {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
    
        int teamSize = 0;
        while (teamSize < 9 || teamSize > 15) {
            System.out.println("How many players do you wish per team?");
            System.out.println("(Enter a value in the range 9 - 15): ");
            teamSize = scan.nextInt();
            if (teamSize < 9 || teamSize > 15) {
                System.out.println("Number of players Invalid.");
            }
        }

        int players = 0;
        while (players < 1) {
            System.out.println("How many players are available?");
            players = scan.nextInt();
            if (players < 1) {
                System.out.println("Number of players Invalid.");
            }
        }

        int teams = players / teamSize;
        int leftOver = players % teamSize;
        System.out.println("There will be " + teams + " teams with " + leftOver + " players left over.");
    }
}