Java 中的生日猜测器，代码行被无缘无故地跳过

Question

我正在做 Y. Daniel Liang 的书 "Introduction to Java Programming" 中的练习。在这个程序中，用户会看到一个 table ，其中包含一个月中的不同日期。如果用户生日在呈现的table中，用户提示'Y'是，'N'不是。根据用户提示的次数 'Y'，程序应该猜测用户生日是一个月中的哪一天。当我运行程序并显示第一组日期时，我输入 'Y' 或 'N'。然后打印 set2 和 3，但我没有输入任何输入。打印set 4时，我可以再次输入，但是打印set 5后，无法输入。为什么我只能在 set1 和 4 之后输入 input？代码如下：

import java.util.Scanner;


public class GuessBirthday {

public static void main(String[] args)
        throws java.io.IOException {

String set1 = 
    "  1  3  5  7\n" +
    "  9 11 13 15\n" +
    " 17 19 21 23\n" + 
    " 25 27 29 31";

    String set2 = 
    "  2  3  6  7\n" +
    " 10 11 14 15\n" +
    " 18 19 22 23\n" + 
    " 26 27 30 31";

    String set3 = 
    "  4  5  6  7\n" +
    " 12 13 14 15\n" +
    " 20 21 22 23\n" + 
    " 28 29 30 31";

    String set4 = 
    "  8  9 10 11\n" +
    " 12 13 14 15\n" +
    " 24 25 26 27\n" + 
    " 28 29 30 31";

    String set5 = 
    " 16 17 18 19\n" +
    " 20 21 22 23\n" +
    " 24 25 26 27\n" + 
    " 28 29 30 31";

    int day = 0;

    // Create a scanner

    Scanner input = new Scanner(System.in);

    // Prompt the user to answer questions

    System.out.print("Is your birthday in set1?\n");
    System.out.print(set1);
    System.out.print("\nEnter (Y) for yes or (N) for no: ");
    char answer = (char) System.in.read();

    if (answer == 'Y')
        day += 1;

    System.out.print("\nIs your birthday in set2?\n");
    System.out.print(set2);
    System.out.print("\nEnter (Y) for yes or (N) for no: ");
    answer = (char) System.in.read();

    if (answer == 'Y')
        day += 2;

    System.out.print("\nIs your birthday in set3?\n");
    System.out.print(set3);
    System.out.print("\nEnter (Y) for yes or (N) for no: ");
    answer = (char) System.in.read();

    if (answer == 'Y')
        day += 4;

    System.out.print("\nIs your birthday in set4?\n");
    System.out.print(set4);
    System.out.print("\nEnter (Y) for yes or (N) for no: ");
    answer = (char) System.in.read();

    if (answer == 'Y')
        day += 8;

    System.out.print("\nIs your birthday in set5?\n");
    System.out.print(set5);
    System.out.print("\nEnter (Y) for yes or (N) for no: ");
    answer = (char) System.in.read();

    if (answer == 'Y')
        day += 16;

    System.out.println("\nYour birthday is " + day + "!");

    }
}

Answer 1

您实际上从未通过调用 System.in.read()

吞噬换行符

Answer 2

您一次只能读取 1 个字符，因为您正在使用 System.in.read()。 carriage-return (\r) and/or 换行符 (\n) 将计为字符。因此，在您的第一次输入中，例如在 windows 上，您输入了 'Y\r\n'，因此 System.in.read() 第一次将得到 'Y'，下一次将收到 '\r'。

您可以使用实例化的 Scanner..

String answer = input.nextLine();
if (answer.equals("Y") {
    // blah
}

Answer 3

我想知道同样的事情（使用 0 和 1 很奇怪）所以对于偶然发现这里的任何其他人，我让它工作（注意 - 你也可以用 'char' 来做到这一点只是替换这个词'String' 与 'char'):

import java.util.Scanner;


public class GuessBirthday
{
public static void main( String [] args )
{

String set1 = 
"  1  3  5  7\n" +
"  9 11 13 15\n" +
" 17 19 21 23\n" + 
" 25 27 29 31";

String set2 = 
"  2  3  6  7\n" +
" 10 11 14 15\n" +
" 18 19 22 23\n" + 
" 26 27 30 31";

String set3 = 
"  4  5  6  7\n" +
" 12 13 14 15\n" +
" 20 21 22 23\n" + 
" 28 29 30 31";

String set4 = 
"  8  9 10 11\n" +
" 12 13 14 15\n" +
" 24 25 26 27\n" + 
" 28 29 30 31";

String set5 = 
" 16 17 18 19\n" +
" 20 21 22 23\n" +
" 24 25 26 27\n" + 
" 28 29 30 31";

int day = 0;

// Create a scanner

Scanner input = new Scanner(System.in);

// Prompt the user to answer questions

System.out.print("Is your birthday in set1?\n");
System.out.print(set1);
System.out.print("\nEnter (Y) for yes or (N) for no: ");
String answer = input.next();

if (answer.equals("Y"))
    day += 1;

System.out.print("\nIs your birthday in set2?\n");
System.out.print(set2);
System.out.print("\nEnter (Y) for yes or (N) for no: ");
answer = input.next();

if (answer.equals("Y"))
    day += 2;

System.out.print("\nIs your birthday in set3?\n");
System.out.print(set3);
System.out.print("\nEnter (Y) for yes or (N) for no: ");
answer = input.next();

if (answer.equals("Y"))
    day += 4;

System.out.print("\nIs your birthday in set4?\n");
System.out.print(set4);
System.out.print("\nEnter (Y) for yes or (N) for no: ");
answer = input.next();

if (answer.equals("Y"))
    day += 8;

System.out.print("\nIs your birthday in set5?\n");
System.out.print(set5);
System.out.print("\nEnter (Y) for yes or (N) for no: ");
answer = input.next();

if (answer.equals("Y"))
    day += 16;

System.out.println("\nYour birthday is " + day + "!");

}
}

Java 中的生日猜测器，代码行被无缘无故地跳过

Birthday guesser in Java, code lines are skipped for no obvious reason

java

string

input

character