NoSuchElementException try/catchブロック内のスキャナで

Question

2つの可能なゲームモードを持つ単純な迷路ゲームでは、スキャナを使用してプレーヤーの名前を尋ねた後、ゲームの開始時にスキャナを実装しようとしています。私はクラスMenuParserを作ることにしました。オブジェクトを受け入れ、それぞれのメソッドに渡す静的メソッドを使いたいと思います。一つの理由または別のために

、Javaは同じエラーを返すに保つ：

Exception in thread "main" java.util.NoSuchElementException at java.util.Scanner.throwFor(Unknown Source) at java.util.Scanner.next(Unknown Source) at java.util.Scanner.nextInt(Unknown Source) at java.util.Scanner.nextInt(Unknown Source) at game.MenuParser.startUpMenu(MenuParser.java:26) at game.MainProgram.main(MainProgram.java:18)

私は/試してから値を返すに対処する方法について（this oneまたはthis oneなど）同様の質問を見てきましたブロックをキャッチし、NoSuchElementExceptionとScannerの原因は何ですか、私はそれを把握していないようです。 returnを移動して、Scannerを単純化する（try/catchブロックを単純に削除するなど）ようにしましたが、どちらも問題を解決しません。

ご協力いただければ幸いです。

package game; 

import java.util.InputMismatchException; 
import java.util.Scanner; 

public class Player { 

    private String playerName; 
    private int playerStepScore; 

    public Player() { 
    } 

    public void setPlayerNameWithScanner(){ 

     System.out.println("Please enter your name. \n"); 

     try(Scanner playerNameScanner = new Scanner(System.in);){ 

      String playerName = playerNameScanner.nextLine(); 
      setPlayerName(playerName); 
     } 
     catch(InputMismatchException im) { 
      System.out.println("Input seems to be wrong"); 
      setPlayerNameWithScanner(); 
     } 
    } 

    public String getPlayerName() { 
     return playerName; 
    } 
    public void setPlayerName(String playerName) { 
     this.playerName = playerName; 
    } 
    public int getPlayerStepScore() { 
     return playerStepScore; 
    } 
    public void setPlayerStepScore(int playerStepScore) { 
     this.playerStepScore = playerStepScore; 
    } 


} 

前のmainメソッドを次のように

package game; 

import java.util.InputMismatchException; 
import java.util.Scanner; 

public class MenuParser { 

    public static void pause() { 

     System.out.println("Please hit enter to continue."); 
     Scanner hitEnter = new Scanner(System.in); 
     hitEnter.nextLine(); 
     hitEnter.close(); 
    } 

    public static int startUpMenu() { 

     int choice = 0; 

     System.out.println("Which game mode would you like to play?" + "\n"); 
     System.out.println("\t 1. Single player."); 
     System.out.println("\t 2. Robot."); 

     try(Scanner startUp = new Scanner(System.in)){ 

      choice = startUp.nextInt(); 
      System.out.println(choice); 

      if(choice != 1 || choice != 2) { 

       System.out.println("Sorry, this is not a valid choice."); 
       startUpMenu(); 
      } 
     } 
     catch(InputMismatchException im) { 

      System.out.println("Sorry, it seems the input is of wrong type."); 
      startUpMenu(); 
     } 
     return choice; 
    } 
} 

プレーヤークラスが見えます：次のように

package game; 

import world.Maze; 

public class MainProgram { 

    public static void main(String[] args) { 

     // Initialize objects concerned with playing the game 
     Player myPlayer = new Player(); 
     Maze myMaze = new Maze(); 

     // Print welcome message and ask the player for his/her name 
     System.out.println("Hi there! Welcome to this maze game in Java by MV. \n"); 
     myPlayer.setPlayerNameWithScanner(); 

     // Ask the player which game mode he/she would like to play: single player or multiplayer? 
     int choice = MenuParser.startUpMenu(); 
     System.out.println(choice); 
     // Parse input and depending on the answer initialize the corresponding menu to start the game 
    } 

} 

MenuParserクラスが見えます：次のように

mainメソッドが見えます（try-with-recourcesを含む複数のスキャナーを使用していて、エラーや例外なしで）次の：

package game; 

import java.util.Scanner; 
import java.io.FileNotFoundException; 
import java.io.FileReader; 
import game.Cell; 
import game.Maze; 
import game.Border; 

public class Program { 

    public static void main(String[] args) { 

     /* 
     * General variables that will be used throughout the loops 
     * that follow; maxXCoor and maxYCoor are used as maximum values 
     * to initialize a grid of a certain size; myMaze is a Maze object 
     * which is needed to access its methods throughout the loops. 
     */ 
     int maxXCoor = 0; 
     int maxYCoor = 0; 
     Maze myMaze = new Maze(); 

     /* 
     * A Scanner is invoked to simply deal with the entry 
     * of the file name; this location is then saved in the 
     * variable fileName, which is then passed onto the next 
     * Scanner and FileReader. 
     */ 
     System.out.println("Please enter a file name"); 
     Scanner scan = new Scanner(System.in); 
     String fileName = scan.nextLine(); 
     scan.close(); 
     System.out.println(fileName); 

     /* 
     * This first block is used to scan the entire input file 
     * and look for maxXCoor and maxYCoor to initialize the grid. 
     */ 
     try(Scanner input = new Scanner(new FileReader(fileName));){ 

      int count = 1; 
      while(input.hasNextLine()) { 

       /* 
       * Every line is read as a String which is then 
       * split using a comma as the delimiter. Every 
       * part that is delimited by a comma is then put into an 
       * array called words. 
       */ 
       String line = input.nextLine(); 
       String[] words = line.split(","); 

       /* 
       * Basic sanity check to make sure the input file uses 
       * the template which was agreed upon, where the first line 
       * are just headers. 
       */ 
       if(count == 1) { 

        if(!(words[0].toLowerCase()).equals("xcoordinate")) { 

         System.out.println("It looks like there is an issue with the template of your input file."); 
         System.out.println("Please check your input file and try again!"); 
         System.exit(0); 
        } 
       } 
       /* 
       * Once we're not at line one anymore, we can start checking 
       * the current coordinates, xCoor and yCoor, against 
       * the maximum coordinates, maxXCoor and maxYCoor. 
       */ 
       else { 

        int xCoor = Integer.parseInt(words[0]); 
        int yCoor = Integer.parseInt(words[1]); 

        if(xCoor > maxXCoor) { 

         maxXCoor = xCoor; 
        } 
        if(yCoor > maxYCoor) { 

         maxYCoor = yCoor; 
        } 
       } 
       count++; 
      } 
     } 
     catch(FileNotFoundException fe) { 
      System.out.println("File not found"); 
      System.exit(0); 
     } 

     /* 
     * As Java uses zero-indexing, we will want to 
     * augment the values of our maximum coordinates 
     * by one, to avoid IndexOutOfBoundsExceptions in 
     * the future. After that we initialize a 2D array 
     * of type Cell with these coordinates. 
     */ 
     maxXCoor++; 
     maxYCoor++; 
     Cell[][] myGrid = new Cell[maxXCoor][maxYCoor]; 


     try(Scanner input = new Scanner(new FileReader(fileName));){ 

      int count = 1; 
      while(input.hasNextLine()) { 

       String line = input.nextLine(); 
       String[] words = line.split(","); 

       if(count > 1) { 

        int xCoor = Integer.parseInt(words[0]); 
        int yCoor = Integer.parseInt(words[1]); 
        Border borderNorth = new Border(words[2]); 
        Border borderSouth = new Border(words[3]); 
        Border borderEast = new Border(words[4]); 
        Border borderWest = new Border(words[5]); 
        Cell myCell = new Cell(borderNorth,borderSouth,borderEast,borderWest); 
        myGrid[xCoor][yCoor] = myCell; 

       } 
       count++; 
      } 
     } 
     catch(FileNotFoundException fe) { 
      System.out.println("File not found"); 
      System.exit(0); 
     } 

     for(int x = maxXCoor-1; x >= 0; x--) { 
      // Draw north & south wall 
      for(int y = 0; y < maxYCoor; y++) { 
       Border myBorderNorth = myGrid[x][y].getNorthWall(); 
       String myTypeNorth = myBorderNorth.getType(); 
       if(myTypeNorth.equals("wall")) { 
        System.out.print("+---"); 
       } 
       else { 
        System.out.print("+ "); 
       } 
       if(y == maxYCoor-1) { 
        System.out.println("+"); 
       } 
      } 
      // Draw west & east wall 
      for(int y = 0; y < maxYCoor; y++) { 
       Border myBorderWest = myGrid[x][y].getWestWall(); 
       String myTypeWest = myBorderWest.getType(); 
       if(myTypeWest.equals("wall")) { 
        System.out.print("| "); 
       } 
       else { 
        System.out.print(" "); 
       } 
       // Draw last eastern wall 
       if(y == maxYCoor-1) { 
        System.out.println("|");      
       } 
      } 
      // Draw last southern wall 
      if(x == 0) { 
       for(int y = 0; y < maxYCoor; y++) { 
        System.out.print("+---"); 
       } 
       System.out.println("+"); 
      } 
     } 
     myMaze.setGrid(myGrid); 
    } 

} 

Answer 1

あなたはこのコードを持っている：

 try(Scanner startUp = new Scanner(System.in)){ 
      //stuff 
     } 

これは試してみる-と資源として知られています。このtryブロックの実行が終了すると、コードはスキャナを自動的に閉じます。

ただし、System.inに関連付けられたスキャナを閉じると、System.inは閉じたままです。新しいScannerを使用した場合でも、他のものを読むと、NoSuchElementExceptionが表示されます。それはここで起こっているようです。ほとんどの場合、setPlayerNameWithScannerは同様の方法でスキャナを終了しているため、問題が発生しています。