每当我运行此命令时,chooseCave()
函数就可以与in.nextInt()
一起正常工作。当我选择洞穴时,消息会每隔2秒弹出一次,然后当它越过该部分时,就会出现错误:
Exception in thread "main" java.util.NoSuchElementException: No line found
at java.util.Scanner.nextLine(Unknown Source)
at Dragon.main(Dragon.java:81)
我尝试了
hasNextLine()
和hasNextInt()
,当我在while hasNextLine()
方法中使用main
时,出现了很多错误。当我在while hasNextInt()
方法中使用chooseCave()
时,它不接受我的输入。当我在
if hasNextInt()
方法中使用chooseCave()
时,它不接受我的playAgain
字符串输入,直接进入另一个游戏,但是hasNextInt()
boolean 值返回false
,并且它无限地向“Which Cave ...”发送垃圾邮件。我已经阅读了错误报告,以及类似问题的Java文档和Stack Overflow。请帮忙。
import java.util.Scanner;
public class Dragon {
public static void displayIntro() {
System.out.println("You are in a land full of dragons. In front of you, ");
System.out.println("You see two caves. In one cave, the dragon is friendly");
System.out.println("and will share his treasure with you. The other dragon");
System.out.println("is greedy and hungry, and will eat you on sight");
System.out.println(' ');
}
public static int chooseCave() {
Scanner in = new Scanner(System.in);
int cave = 0;
while (cave != 1 && cave != 2) {
System.out.println("Which cave will you go into? (1 or 2)");
cave = in.nextInt();
}
in.close();
return cave;
}
public static void checkCave(int chosenCave) {
System.out.println("You approach the cave...");
try
{
// Sleep at least n milliseconds.
// 1 millisecond = 1/1000 of a second.
Thread.sleep( 2000 );
}
catch ( InterruptedException e )
{
System.out.println( "awakened prematurely" );
}
System.out.println("It is dark and spooky...");
try
{
// Sleep at least n milliseconds.
// 1 millisecond = 1/1000 of a second.
Thread.sleep( 2000 );
}
catch ( InterruptedException e )
{
System.out.println( "awakened prematurely" );
}
System.out.println("A large dragon jumps out in front of you! He opens his jaws and...");
try
{
// Sleep at least n milliseconds.
// 1 millisecond = 1/1000 of a second.
Thread.sleep( 2000 );
}
catch ( InterruptedException e )
{
System.out.println( "awakened prematurely" );
}
double friendlyCave = Math.ceil(Math.random() * 2);
if (chosenCave == friendlyCave) {
System.out.println("Gives you his treasure!");
}
else {
System.out.println("Gobbles you down in one bite!");
}
}
public static void main(String[] args) {
Scanner inner = new Scanner(System.in);
String playAgain = "yes";
boolean play = true;
while (play) {
displayIntro();
int caveNumber = chooseCave();
checkCave(caveNumber);
System.out.println("Do you want to play again? (yes or no)");
playAgain = inner.nextLine();
if (playAgain == "yes") {
play = true;
}
else {
play = false;
}
}
inner.close();
}
}
最佳答案
您关闭了第二个Scanner
,后者又关闭了底层的InputStream
,因此第一个Scanner
无法再从相同的InputStream
中读取,并且NoSuchElementException
结果出现。
解决方案:对于控制台应用程序,请使用单个Scanner
从System.in
中读取。
除了:如前所述,请注意Scanner#nextInt
不使用换行符。在尝试使用nextLine
再次调用Scanner#newLine()
之前,请确保已消耗掉它们。
另请:Do not create multiple buffered wrappers on a single InputStream