Question

我要做的是从文件中读取（在这种情况下，文件包含超过100,000行）并将值存储在数组中，然后打印出前10行。然而，当我运行程序时，我得到第一行，然后是9行＆＃34; null＆＃34;这显然不是我想要的！这是代码，任何提示将不胜感激。

import java.io.*;
import java.util.Scanner;

public class DawsonZachA5Q2{
  public static void main(String[] args){

Scanner keyboard = new Scanner(System.in);

 System.out.println("Enter a size for the number of letters for words: ");
int size = keyboard.nextInt();//prompts user for input
String[] array = new String[27000];

    try {
       File file = new File("big-word-list.txt");
      Scanner scanner = new Scanner(file);


        // Start a line count and declare a string to hold our current line.
        int linecount=0;

        // Tells user what we're doing
        System.out.println("Searching for words with " + size + " letters in file...");
        int wordCount=0;

        while (scanner.hasNext()){
          int i = 0;
          String word = scanner.next();

          if(size == word.length()){
            wordCount++;
            array[i]=word;
            i++;
            //add word to array
          // increase the count and find the place of the word
        }
        }

        linecount++;






            System.out.println(wordCount);

            System.out.println(wordCount+" words were found that have "+size+ " letters.");//final output


          for(int o = 0; o<10; o++){
            System.out.println(array[o]);
          }


       scanner.close();
    }// our catch just in case of error
    catch (IOException e) {
        System.out.println("Sorry! File not found!");
    }



  } // main


} // class

Answer 1

在int i = 0;循环之外定义while。每次循环运行时它都会设置为零。这就是问题所在。

Answer 2

你在while循环中犯了错误。您必须在while循环之前定义'int i = 0'。在你的情况下，发生的是每当while循环执行时，i被初始化为0.即每次找到所需长度的单词时，该单词将被存储在数组[0]中（因为我每次迭代都被初始化为0） of while循环）替换先前存储的值。因此，您只获得第一个值并保持显示为null，因为在array [1]之后没有存储任何内容。因此，实际流程应该是这样的。

// i is initialized outside of loop.
int i = 0;
while (scanner.hasNext()){
    //int i = 0;  this is your error
    String word = scanner.next();
    if(size == word.length()){
        wordCount++;
        array[i]=word;
        i++;
        //add word to array
        // increase the count and find the place of the word
    }
}

为什么我得到＆＃34; null＆＃34;作为输出字符串？ Java的

2 个答案: