我遇到了这段代码的问题。它是不完整的，但我现在的目的是测试菜单是否有效，基本上我要做的是实现一个菜单。如果输入了无效字符，请继续提示进行有效选择。提示：在实现其他选项之前实施Quit。似乎无法弄清楚我做错了什么来得到这个错误。
import java.util.Scanner;
public class Playlist
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
String title = "";
System.out.println("Enter playlist's title: ");
title = input.nextLine();
printMenu(title);
}
// Implement the printMenu() method.
// printMenu() takes the playlist title as a parameter and outputs a menu of options to manipulate the playlist.
// Each option is represented by a single character.
// Build and output the menu within the method.
public static void printMenu(String playlistTitle)
{
Scanner input = new Scanner(System.in);
boolean menu = true;
String option;
SongEntry songentry = new SongEntry();
System.out.println(playlistTitle + " PLAYLIST MENU");
System.out.println("a - Add song");
System.out.println("d - Remove song");
System.out.println("c - Change position of song");
System.out.println("s - Output songs by specific artist");
System.out.println("t - Output total time of playlist (in seconds)");
System.out.println("o - Output full playlist");
System.out.println("q - Quit");
System.out.println("");
while(menu == true)
{
System.out.println("Choose an option: ");
switch(option = input.next())
{
case "q":
menu = false;
break;
case "o":
System.out.println(playlistTitle + " - OUTPUT FULL PLAYLIST");
break;
case "a":
System.out.println("ADD SONG");
System.out.println("Enter song's unique ID: ");
System.out.println("Enter song's name: ");
System.out.println("Enter artist's name: ");
System.out.println("Enter song's length: ");
break;
case "d":
System.out.println("REMOVE SONG");
System.out.println("Enter a song's unique ID: ");
System.out.println(" removed");
break;
case "c":
System.out.println("CHANGE POSITION OF SONG");
System.out.println("Enter a song's current position: ");
System.out.println("Enter a new position for song: ");
System.out.println(" moved to position ");
break;
case "s":
System.out.println("OUTPUT SONGS BY SPECIFIC ARTIST");
System.out.println("Enter artist's name: ");
break;
case "t":
System.out.println("OUTPUT TOTAL TIME OF PLAYLIST (IN SECONDS)");
System.out.println("Total time: seconds");
break;
}
}
}
}
当我运行它时，我得到：
线程中的异常＆＃34; main＆＃34; java.util.Scanner.throwFor（Scanner.java:907）中的java.util.NoSuchElementException，位于Playlist.printMenu（Playlist.java:45）的java.util.Scanner.next（Scanner.java:1416） Playlist.main（Playlist.java:12）
感谢您的帮助。
答案 0 :(得分：0)
在调用方法之前尝试关闭扫描仪，输入开关时打开两个扫描仪
答案 1 :(得分：0)
我实际上发现我需要将Scanner传递给printMenu方法。它现在有效。谢谢大家的建议！
import java.util.Scanner;
public class Playlist
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
String title = "";
System.out.println("Enter playlist's title: ");
title = input.nextLine();
printMenu(title, input);
}
// Implement the printMenu() method.
// printMenu() takes the playlist title as a parameter and outputs a menu of options to manipulate the playlist.
// Each option is represented by a single character.
// Build and output the menu within the method.
public static void printMenu(String playlistTitle, Scanner input)
{
boolean menu = true;
String option;
SongEntry songentry = new SongEntry();
System.out.println(playlistTitle + " PLAYLIST MENU");
System.out.println("a - Add song");
System.out.println("d - Remove song");
System.out.println("c - Change position of song");
System.out.println("s - Output songs by specific artist");
System.out.println("t - Output total time of playlist (in seconds)");
System.out.println("o - Output full playlist");
System.out.println("q - Quit");
System.out.println("");
while(menu == true)
{
System.out.println("Choose an option: ");
switch(option = input.next())
{
case "q":
menu = false;
break;
case "o":
System.out.println(playlistTitle + " - OUTPUT FULL PLAYLIST");
break;
case "a":
System.out.println("ADD SONG");
System.out.println("Enter song's unique ID: ");
System.out.println("Enter song's name: ");
System.out.println("Enter artist's name: ");
System.out.println("Enter song's length: ");
break;
case "d":
System.out.println("REMOVE SONG");
System.out.println("Enter a song's unique ID: ");
System.out.println(" removed");
break;
case "c":
System.out.println("CHANGE POSITION OF SONG");
System.out.println("Enter a song's current position: ");
System.out.println("Enter a new position for song: ");
System.out.println(" moved to position ");
break;
case "s":
System.out.println("OUTPUT SONGS BY SPECIFIC ARTIST");
System.out.println("Enter artist's name: ");
break;
case "t":
System.out.println("OUTPUT TOTAL TIME OF PLAYLIST (IN SECONDS)");
System.out.println("Total time: seconds");
break;
}
}
}
}