在 java 中传入 args[] 或缺少 args

Question

我正在为 class 中的作业编写代码，并且从未以这种方式实际使用过扫描器。然而，当我朗读下面的代码时，我得到了错误

Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextInt(Scanner.java:2117)
at java.util.Scanner.nextInt(Scanner.java:2076)
at World.<init>(World.java:20)
at World.main(World.java:58)

我想我只是很困惑，因为我有 eclipse 使用世界文本文件来创建，它只是不允许它。

   import java.util.Scanner;

 /*************************************************************************
* Name        :  
* Username    : 
* Description :      *************************************************************************/

 public class World{
//instance variables
String mapFile; //This holds the .txt name that contains the map.
Tile[][] worldMap;

public World(String mapFile){
    this.mapFile = mapFile;

    Scanner scanner = new Scanner(mapFile);
    //get the dimensions of the world
    int width = scanner.nextInt();
    int height = scanner.nextInt();
    int x_coor = scanner.nextInt();
    int y_coor = scanner.nextInt();
    //initialize the array to proper height and width
    worldMap = new Tile[width][height];
    //set the starting locations of the avatar character
    Avatar avatar = new Avatar(x_coor, y_coor);
    //populate the worldMap
    for(int i = 0; i < worldMap.length - 1; i++){
        for(int j = 0; i <worldMap[0].length -1; j++){
            worldMap[i][j] = new Tile(scanner.next());
        }
    }


}
//draw the map
public void draw(){
    for(int i = 0; i < worldMap.length - 1; i++){
        for(int j = 0; j < worldMap[0].length -1; i++){
            worldMap[i][j].draw(i, j);
        }
    }
}







// Test method


public static void main(String [] args)
{       


    World world = new World(args[0]);
    world.draw();       
}

}

Answer 1

您围绕 String（而不是 File）构建了 Scanner。改变这个

Scanner scanner = new Scanner(mapFile);

至

Scanner scanner = new Scanner(new File(mapFile));

现在 Scanner 正在扫描您的 String 文件名。

在 java 中传入 args[] 或缺少 args

passing in args[] or missing args in java

java

arguments

file

external