java - 在 Java 中打印一段单词中的每个单词，同时使用 Scanner 类跳过一些单词

Question

我正在编写一个程序来接收文件并输出文件。 输入文件包含如下内容:

    1 cat dog rabbit
    3 cat dog rabbit rabbit rabbit
    2 yellow red blue white black
    0 three two one

输出文件为:

    dog rabbit rabbit rabbit blue white black three two one

(程序接受每行开头的整数，然后跳过每行的单词数，然后保存其余单词并输出到文件)

最初，我有

import java.util.Scanner;
import java.io.FileNotFoundException;
import java.io.File;
import java.io.PrintWriter;

public class Scanner2{
    public static void main(String args[]) {
        String c = "";
        try{
            File file = new File(args[0]);
            Scanner scanner = new Scanner(file); 
            PrintWriter writer = new PrintWriter(args[1]);
        // as long as the scanner reads that the file has a next line
               while (scanner.hasNextLine()) {    
        // read the next line of string as string s
                   String s = scanner.nextLine(); 
        // split each word from the string s as an array called "words"
                   String[] words = s.split(" ");
        // for loop executed length of "words" times
                   for(int x = 0; x < words.length; x++) {
        // declare int, "count"
                       int count;
        // parse the first element (the number) from "words" to be an integer, "count"
                       count = Integer.parseInt(words[0]);
        // if the loop is executed more than "count" number of times
                       if (x > count){
        // add respective element to string, "c"
                           c += words[x];
                           c += " ";
                    }
                }
            }
        // close the scanner
            scanner.close();
        // output string "c" to the output file
            writer.println(c);
        // close the writer
            writer.close();
    }
        catch (FileNotFoundException e) {
            e.printStackTrace();
   }      
   }
}

这些代码工作得很好。 但是，现在我想从使用 split 方法切换到另一个第二个扫描器类来读取每个句子的每个单词。

import java.util.Scanner;
import java.io.FileNotFoundException;
import java.io.File;
import java.io.PrintWriter;

public class ScannerDemo{
     public static void main(String args[]) {
        String c = "";
        try{
            File file = new File(args[0]);
            Scanner scanner = new Scanner(file);
            PrintWriter writer = new PrintWriter(args[1]);
         // as long as the scanner reads that the file has a next line
               while (scanner.hasNextLine()) {
        // read the first line of string in scanner s2
                   Scanner s2 = new Scanner(scanner.nextLine());
        // read the first word of first line from s2 as string "counts"
                   String counts = s2.next();
        // parse the string "counts" as int, "count"
                   int count = Integer.parseInt(counts);
        // as long as s2 has the next element
                   while (s2.hasNext()){
        // for loop executed "count" number of times to skip the words
                       for (int x = 0; x < count; x ++){
                           String b = s2.next();
                        }
       // else add the next words to string, "c"
                           c += s2.next();
                           c += " ";
                        }
                    }
        // close the scanner
            scanner.close();
        // output string "c" to the output file
            writer.println(c);
        // close the writer
            writer.close();
        }
        catch (FileNotFoundException e) {
            e.printStackTrace();
  } 

  }
 }

但是，它给出了错误消息

线程“main”中的异常java.util.NoSuchElementException

我认为此错误消息是由于第二个扫描仪类未正确关闭所致。但是我添加后并没有弄清楚如何解决

s2.close();

在 for 循环中。

感谢任何帮助。谢谢，但我对 Java 真的很陌生，

Answer 1

嵌套的 while 和 for 循环中存在一个错误，导致 for 循环中的 s2.next() 超出行尾。尝试如下

            // parse the string "counts" as int, "count"
            int count = Integer.parseInt(counts);
            // for loop executed "count" number of times to skip the words
            for (int x = 0; x < count && s2.hasNext(); x++){
                String b = s2.next();
            }
            // as long as s2 has the next element add the next words to string
            while (s2.hasNext()) {
                c += s2.next();
                c += " ";
            }

此外，建议使用try with resources而不是自行关闭。简化示例:

    try (Scanner scanner = new Scanner(file);
         PrintWriter writer = new PrintWriter(args[1]);) {
        scanner.next();   
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

这样，即使抛出异常，扫描器和编写器也会自动关闭。