Question

我写了这个叫做足球队烘焙师的程序。它存储球员的球衣号码和球员评分。然后在菜单选项中执行用户想要做的事情。但由于某种原因，菜单选项继续打印两次。我被告知它是因为当我要求PlayerRating[i]的int输入时，当我第一次要求用户输入String“menuOption”时，它会接受Enter按钮和输入。有人可以帮忙吗？

这是代码

import java.util.Scanner;

public class SoccerTeamRoaster {

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

        final int JERSY_NUMS = 5;
        int[] JersyNumber = new int[JERSY_NUMS];
        int[] PlayerRating = new int[JERSY_NUMS];
        String[] jPut = new String[JERSY_NUMS];
        int i = 0;
        boolean quit = false;
        for (i = 0; i < JERSY_NUMS; i++) {
            System.out.println("Enter player " + (i + 1) + "'s jersey number: ");
            JersyNumber[i] = sc.nextInt();
            System.out.println("Enter player " + (i + 1) + "'s rating: ");

            PlayerRating[i] = sc.nextInt();
            System.out.println("");

        }

        System.out.println("");
        System.out.println("ROSTER");
        int N = 0;
        for (N = 0; N < JERSY_NUMS; N++) {
            System.out.println("Player " + (N + 1) + " -- Jersey number: " + JersyNumber[N] + ", Rating: " + PlayerRating[N]);
        }

        while (!quit) {
            String Stg = "MENU\n"
                    + "u - Update player rating\n"
                    + "a - Output players above a rating\n"
                    + "r - Replace player\n"
                    + "o - Output roster\n"
                    + "q - Quit\n";
            System.out.println("");
            System.out.println(Stg);
            System.out.println("Choose an option: ");
            String menuOption = "?";
            menuOption = sc.nextLine();

            boolean correctInput = false;
            if (menuOption.equals("u") || menuOption.equals("a") || menuOption.equals("r") || menuOption.equals("o") || menuOption.equals("q")) {
                correctInput = true;
                menuOption = menuOption.trim();
            } else {
                correctInput = false;
            }

            if (menuOption.equals("u")) {
                System.out.println("Enter jersey number: ");
                int jerseyNum = sc.nextInt();

                System.out.println("New rating for player: ");
                int newRate = sc.nextInt();
                int M = 0;
                for (M = 0; M < JERSY_NUMS; M++) {

                    if (JersyNumber[M] == jerseyNum) {
                        PlayerRating[M] = newRate;
                    }
                }
            } else if (menuOption.equals("a")) {
                System.out.println("Enter a rating: ");
                int rating = sc.nextInt();
                int k = 0;
                for (k = 0; k < JERSY_NUMS; k++) {
                    if (PlayerRating[k] > rating) {
                        System.out.println("Player " + (k + 1) + " -- Jersey Number: " + JersyNumber[k] + ", Rating: " + PlayerRating[k]);
                    }
                }

            } else if (menuOption.equals("o")) {
                System.out.println("ROSTER");
                int J = 0;
                for (J = 0; J < JERSY_NUMS; J++) {
                    System.out.println("Player " + (J + 1) + " -- Jersey number: " + JersyNumber[J] + ", Rating: " + PlayerRating[J]);
                }
            } else if (menuOption.equals("q")) {
                quit = true;
            } else if (menuOption.equals("r")) {
                System.out.println("Enter jersey number: ");
                int jerNum = sc.nextInt();
                int l = 0;
                for (l = 0; l < JERSY_NUMS; l++) {
                    if (JersyNumber[l] == jerNum) {
                        System.out.println("Enter new jersey number: ");
                        JersyNumber[l] = sc.nextInt();
                        System.out.println("Enter new player rating: ");
                        PlayerRating[l] = sc.nextInt();
                    }
                }
                int a = 0;
                for (a = 0; a < JERSY_NUMS; a++) {

                    System.out.println("Player " + (a + 1) + " -- Jersey number: " + JersyNumber[a] + ", Rating: " + PlayerRating[a]);
                }

            }

        }

        return;
    }

}

Answer 1

它打印两次的原因是因为这段代码...

menuOption = sc.nextLine();

将其更改为

menuOption = sc.next();

现在，它只打印一次

Answer 2

您使用Scanner#nextInt获取球衣号码和费率。但是Scanner#nextInt不消耗输入的最后一个换行符，因此在此之后调用Scanner＃nextLine时会消耗该换行符。

所以你必须调用Scanner#nextLine一次，以便在while循环之前抛出换行符。

我的while循环打印菜单两次

2 个答案: