从阅读txt文件的java扫描器

Question

二维数组，我不断收到：

java.util.InputMismatchException 
at java.util.Scanner.throwFor(Scanner.java:909) 
at java.util.Scanner.next(Scanner.java:1530) 
at java.util.Scanner.nextInt(Scanner.java:2160) 
at java.util.Scanner.nextInt(Scanner.java:2119) 
at Driver0.readFile(Driver0.java:38) 
at Driver0.main(Driver0.java:18) 

尝试使用扫描仪类，因为它是我所知道的这么远。任何帮助赞赏。试图读取二维数组，但它从来没有完全读取它。我的input.txt的文件是：

-3 -1 0 1 5

import java.io.*; 
import java.util.*; 
public class Driver0 { 
//public static String fileName; // declare so it may be used outside of main 
public static int[][] array; // declare as empty until given dimensions 
public static int dimensionA, dimensionB; // dimensions used in methods 
public static void main(String[] args) { 
    Scanner input = new Scanner(System.in); 
    System.out.println("What is the name of the data file?"); 
    System.out.print("> "); 
    String fileName = input.nextLine(); 
    readFile(fileName); 
    String nextCommand = ""; 
    while (!(nextCommand.equals("quit"))) { 
     System.out.println("\nNext command"); 
     System.out.print("> "); 
     nextCommand = input.nextLine(); 
     choice (nextCommand); 
    } 
} 
public static void choice(String command) { 
    switch (command) { 
     case "help": System.out.println("show array\nrows sorted\ncols sorted"+ 
        "increase row i by n\nincrease col j by n\nquit\n"); 
       break; 
     default: showArray(); 
    } 
} 
public static void readFile(String fileName) { 
    try { 
     Scanner foo = new Scanner(fileName); 
     dimensionA = foo.nextInt(); 
     dimensionB = foo.nextInt(); 

     array = new int[dimensionA][dimensionB]; 
     while (foo.hasNext()) { 
      for (int row = 0; row < dimensionA; row++) { 
       foo.nextLine(); 
       for (int column = 0; column < dimensionB; column++) { 
        array[row][column] = foo.nextInt(); 
       } 
      } 
     } 
     foo.close(); 
    } 
    catch(Exception e) { 
     e.printStackTrace(); // displays type of error 
    } 
} 
public static void showArray() { 
    for (int ro = 0; ro < dimensionA; ro++) { 
     for (int col = 0; col < dimensionB; col++) { 
      System.out.print(array[ro][col]); 
     } 
     System.out.println(); 
    } 
} 
} 

Answer 1

转到通过Scanner类中的方法。

特别是，hasXXX()和nextXXX()方法，他们成对出现。尽量不要混合匹配那些使事情变得复杂的方法。您正在使用nextInt(),hasNext()和nextLine()。文档还解释了这些方法在调用它们时的作用。

对于您的情况，如果您愿意使用String.split()，方法hasNextLine()和nextLine()就足够了。您可以拆分nextLine()返回的字符串，并分析整数并将其分配给数组元素。

Answer 2

我认为最好使用ArrayList。试试这个

package readfile; 

import java.io.BufferedReader; 
import java.io.FileNotFoundException; 
import java.io.FileReader; 
import java.io.IOException; 
import java.util.ArrayList; 
import java.util.List; 

public class Read { 

public static void main(String[] args) throws FileNotFoundException, IOException { 

    String line = null; 
    List<String[]> list = new ArrayList<String[]>(); 
    BufferedReader reader = new BufferedReader(new FileReader("/home/user/My_Folder/read_me.txt")); 
    while ((line = reader.readLine())!=null) { 
     list.add(getArray(line)); 
    }   
    reader.close(); 

    for (String[] stringArr : list) { 
     for(String str : stringArr){ 
      System.out.print(str+" "); 
     } 
     System.out.println(""); 
    } 

} 

private static String[] getArray(String s){ 
    String[] array = s.split("\\s"); 
    return array; 
} 

}