Question

我写了一个代码，它获取了一个文本文件作为输入，然后程序使用文本制作相等的String数组，这样可以比较单词并查找+计算唯一和重复的单词。该程序成功编译，但如果我尝试执行它，所以我得到问题：线程“main”中的异常java.lang.NullPointerException ... java：52。问题必须在于我声明字符串的方式。我该怎么写呢？谢谢！

import java.util.*;

class TextAnalyze{
public static void main(String[] args){
In read = new In ("text1.txt"); //input *.txt file

    int tWords = 0; // counter, total words in the text file
    int unW = 0; //counter UNIQUE words in the text file
    String[] word = new String[31000]; //array with all the words
    String[] word2 = new String[31000]; // array with all the words, used to compare
    //String uniqueWords[] = new String[31000]; //array with the unique words
    //int numberuniqueWords[] = new int [31000];

    while(read.endOfFile() == false) {

        word[tWords] = read.inWord();
        word2[tWords] = word[tWords];
        tWords++;

    }

    int totalWords = word.length;
    int totalWords2 = word2.length;

    List<String> uniqueWords = new ArrayList<>();

    for (int i = 0; i < totalWords; i++) { // loop of the first array list
        boolean unique = true;

        for (int j = 0; j < totalWords2; j++) { // second loop where the
                                        // words are being compared
            if (word[i].equals(word2[j])) {
                //we find two equals strings, it not unique
                unique = false;
                break;
            }
        }

        //if it remains unique there wasn't equals
        if (unique) {
            uniqueWords.add(word[i]);
        }
    }

    for (String s : uniqueWords) {
        System.out.println(s);
    }

}

}

Answer 1

int totalWords = word.length;

这可能是你的问题。数组的长度是它的容量，而不是放在其中的实际对象数。因此，它将始终返回31000.如果这不是文本文件中的单词数，那么您的循环将从数组中提取空值。

Answer 2

我认为@Aurand已经发现了这个问题。您现在可以对比较进行空检查：

if(word[i] != null && word2[j] != null){
            if (word[i].equals(word2[j])) {
                //we find two equals strings, it not unique
                unique = false;
                break;
            }
}

Answer 3

        FileReader fr = new FileReader("/home/rajesh/Desktop/movie");
        BufferedReader br = new BufferedReader(fr);
        String s;
        Set<String> sdata = new HashSet<String>();
        List<String> adata = new ArrayList<String>();
        while ((s = br.readLine()) != null) {
            for (String val : s.split(" ")) {
                sdata.add(val);
                adata.add(val);
            }
        }

        for (String val : sdata) {    
            int freq = Collections.frequency(adata, val);
            System.out.println("Frequency of " + val + " " + freq);
        }

如果要在命令模式下运行此代码，则必须指定try catch block或throws。

Answer 4

import java.util.Vector;
import java.util.Scanner;

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

Scanner in = new Scanner(System.in);    
System.out.print("enter a text? ");
String txt = in.nextLine();

Vector<Character> ch = new Vector<Character>();
char len[] = txt.toCharArray();
int count;

for(int i=0; i<len.length; i++){
count=0;
for(int j=0; j<len.length; j++){
    if(len[i]==len[j]){
    count++;
    }
}

if(count>0){
    if(!ch.contains(len[i])){
    System.out.println(len[i] + " - " + count);
    ch.add(len[i]);
    }
    }
}


}
}

用于查找和计算文本中重复单词的程序。字符串写错了？

4 个答案: