java: input.next 不再接受用户输入

Posted 2023-02-25

【中文标题】java: input.next 不再接受用户输入

【英文标题】：java: input.next no longer accepting user input

【发布时间】：2016-02-03 05:09:54

【问题描述】：

我修复了大部分新问题，但现在我在线收到一个空字符文字和未闭合字符文字错误：char a = input.next('');

以下是我的新代码，但我不完全确定如何修复此错误。

import java.util.*;
import java.io.BufferedReader;
public class JesseSabatinihw 
    public static void main(String[] args) 
        Scanner input = new Scanner(System.in);
        char lottoGameSelection; // user inputs whether or not they want to play the Lottery Game
        int game; // user input of game 3, 4, or 5 as integer
        int times; // user input of times game is played as integer
        int randNum; // random number generator creates an integer
        int lotNum; //lottery number generated as an integer
        int sum = 0; // initializing the sum of all integers as 0 to start with

        System.out.println("Do you wish to make lottery game selections?");
        char a = input.next('');
        if(a == 'Y' || a =='y')        
            System.out.println("Which lottery game do you want to play!");
            System.out.println("Enter 3 for Pick 3");
            System.out.println("Enter 4 for Pick 4");
            System.out.println("Enter 5 for Pick 5");
            game = input.nextInt();

            System.out.print("How many games would you like to play? ");
            times = input.nextInt();
            System.out.println("Thank you! The numbers selected were: ");
            // generates random lottery number specific to the chosen game 3, 4, or 5 numbers per games specified by user input
            Set<Integer> numbers = new HashSet<>();
            for(int i = 0; i < times; i++) 
                lotNum = 0;
                for(int j = 0; j < game; j++) 
                    do 
                        randNum = (new java.util.Random()).nextInt(10); // calls on the java.util.Random class to randomly select number for game
                    // prevents the generation of duplicate numbers per game
                     while (numbers.contains(randNum));
                    numbers.add(randNum);
                    lotNum = (lotNum * 10) + randNum; // selects random integers 0 - 9
                    System.out.print(randNum); // prints randomly generated number
                    sum += randNum; // adds all random numbers generated
                
                numbers.clear(); // refreshes the number generator preventing duplication of numbers and preventing the code to stop if all int 0-9 are used previously
                System.out.println(); // prints each game on it's own line
            
            System.out.println("Sum of the numbers of all games: " + sum); //prints the total of all randomly generated lottery numbers
         else 
            if (a == 'N' || a == 'n'); 
                System.exit(0);
            
        
    

【问题讨论】：

不要将文本作为图像发布。坚持以文本格式发布输出/代码/数据。

【参考方案1】：

您可以使用 Set 来存储您已经获得的数字，然后重新绘制，直到您获得一个不在 Set 中的数字。

System.out.println("Thank you! The numbers selected were: ");
Set<Integer> numbers = new HashSet<>();
for(int i = 0; i < times; i++) 
  lotNum = 0;
  for(int j = 0; j < game; j++) 
    do 
      randNum = (new java.util.Random()).nextInt(10);
     while (numbers.contains(randNum));
    numbers.add(randNum);
    lotNum = (lotNum * 10) + randNum;
    System.out.print(randNum);
    sum += randNum;
  
  numbers.clear();
  System.out.println();

我不确定您希望数字在什么范围内是唯一的，因此您可能必须在外部循环内创建集合 - 或者在您想要重置它时调用 number.clear()。

【讨论】：

我会继续测试一下，但感谢您的回复。我不知道您是否能够看到我的图像，这是一个示例输出，但基本上，每一行都会生成选择的游戏，因此例如，如果您选择游戏 3 并玩两次，输出将如下所示：123 234我要防止的是每行重复。例如：223 445 等....希望您提供的解决方案可以防止这种情况发生，我非常感谢您的回复！

所以在编辑我的代码并添加您建议的内容后，我没有重复，但是由于没有重复，它会在使用所有 int 0-9 后停止代码并且不打印总和，例如：游戏 3 5 游戏：023 146 578 9 这将是输出，它会停在那里，所以一方面我没有得到重复，这很棒，但另一方面，如果输入请求输出，它不再做我需要的事情生成超过 0-9 ..... 如果有意义的话

好吧，您将随机数限制为 0-9，并且您不希望重复，因此除非您扩大 Random 对象为您提供的数字范围，否则您无法生成更多。跨度>

哦，等等，我想我明白你想说什么了。我认为你必须在每场比赛后清空 Set，所以在内部 for 循环之后调用 numbers.clear() 。我更新了我的代码。

太棒了，我添加了 numbers.clear();现在它可以完美运行了！非常感谢！

【参考方案2】：

所以我终于修好了它并让它完全按照我想要的方式工作 见下文：

import java.util.*;
import java.io.*;
public class JesseSabatinihw2 
    public static void main(String[] args) 
        Scanner input = new Scanner(System.in);
        char lottoGameSelection; // user inputs whether or not they want to play the Lottery Game
        int game; // user input of game 3, 4, or 5 as integer
        int times; // user input of times game is played as integer
        int randNum; // random number generator creates an integer
        int lotNum; //lottery number generated as an integer
        int sum = 0; // initializing the sum of all integers as 0 to start with

        System.out.println("Do you wish to make lottery game selections? Press Y or y for yes and N or n for no.");
        char a = input.next().trim().charAt(0);
        if(a == 'Y' || a == 'y')        
            System.out.println("Which lottery game do you want to play!");
            System.out.println("Enter 3 for Pick 3");
            System.out.println("Enter 4 for Pick 4");
            System.out.println("Enter 5 for Pick 5");
            game = input.nextInt();

            System.out.print("How many games would you like to play? ");
            times = input.nextInt();
            System.out.println("Thank you! The numbers selected were: ");
            // generates random lottery number specific to the chosen game 3, 4, or 5 numbers per games specified by user input
            Set<Integer> numbers = new HashSet<>();
            for(int i = 0; i < times; i++) 
                lotNum = 0;
                for(int j = 0; j < game; j++) 
                    do 
                        randNum = (new java.util.Random()).nextInt(10); // calls on the java.util.Random class to randomly select number for game
                    // prevents the generation of duplicate numbers per game
                     while (numbers.contains(randNum));
                    numbers.add(randNum);
                    lotNum = (lotNum * 10) + randNum; // selects random integers 0 - 9
                    System.out.print(randNum); // prints randomly generated number
                    sum += randNum; // adds all random numbers generated
                
                numbers.clear(); // refreshes the number generator preventing duplication of numbers and preventing the code to stop if all int 0-9 are used previously
                System.out.println(); // prints each game on it's own line
            
            System.out.println("Sum of the numbers of all games: " + sum); //prints the total of all randomly generated lottery numbers
         else 
             if (a == 'N' || a == 'n'); 
                System.exit(0);