java 如何使用java在文件中搜索单词
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How to search for a word in a file using java
提问by Jevison7x
I am writing a java program to search for a word in a text file containing a list of words in the dictionary. As you may now, this file contains about 300,000 words. I was able to come up with a program that can iterate through the words comparing each word with the input word (the word I am searching for). The problem is that this process takes a lot of time to find a word especially if the word starts with the last alphabets like x, y, or z. I want something more efficient that can find a word almost instantly. Here is my code:
我正在编写一个 java 程序来在包含字典中单词列表的文本文件中搜索一个单词。正如您现在可能看到的，这个文件包含大约 300,000 个单词。我能够想出一个程序，它可以遍历单词，将每个单词与输入单词（我正在搜索的单词）进行比较。问题是这个过程需要很多时间来查找一个单词，特别是如果这个单词以 x、y 或 z 等最后一个字母开头。我想要一些更有效的东西，几乎可以立即找到一个词。这是我的代码：
import java.io.IOException;
import java.io.InputStreamReader;
public class ReadFile
{
public static void main(String[] args) throws IOException
{
ReadFile rf = new ReadFile();
rf.searchWord(args[0]);
}
private void searchWord(String token) throws IOException
{
InputStreamReader reader = new InputStreamReader(
getClass().getResourceAsStream("sowpods.txt"));
String line = null;
// Read a single line from the file. null represents the EOF.
while((line = readLine(reader)) != null && !line.equals(token))
{
System.out.println(line);
}
if(line != null && line.equals(token))
{
System.out.println(token + " WAS FOUND.");
}
else if(line != null && !line.equals(token))
{
System.out.println(token + " WAS NOT FOUND.");
}
else
{
System.out.println(token + " WAS NOT FOUND.");
}
reader.close();
}
private String readLine(InputStreamReader reader) throws IOException
{
// Test whether the end of file has been reached. If so, return null.
int readChar = reader.read();
if(readChar == -1)
{
return null;
}
StringBuffer string = new StringBuffer("");
// Read until end of file or new line
while(readChar != -1 && readChar != '\n')
{
// Append the read character to the string. Some operating systems
// such as Microsoft Windows prepend newline character ('\n') with
// carriage return ('\r'). This is part of the newline character
// and therefore an exception that should not be appended to the
// string.
if(readChar != '\r')
{
string.append((char) readChar);
}
// Read the next character
readChar = reader.read();
}
return string.toString();
}
}
}
Please also note that I would like to use this program in a Java ME environment. Any help would be highly appreciated thanks - Jevison7x.
另请注意，我想在 Java ME 环境中使用此程序。感谢您提供任何帮助 - Jevison7x。
回答by nhahtdh
You can use fgrep(fgrepis activated by -Fto grep) (Linux man page of fgrep):
您可以使用fgrep（fgrep由-Fto激活grep）（fgrep 的 Linux 手册页）：
grep -F -f dictionary.txt inputfile.txt
The dictionary file should contain the words one on each line.
字典文件应包含每行一个单词。
Not sure if it is still accurate, but Wikipedia article on grepmentions the use of Aho-Corasick algorithmin fgrep, which is an algorithm that builds an automata based on a fixed dictionaryfor quick string matching.
不确定它是否仍然准确，但维基百科关于 grep 的文章提到了Aho-Corasick 算法在中的使用fgrep，这是一种基于固定字典构建自动机以进行快速字符串匹配的算法。
Anyway, you can have a look at the list of string searching algorithms on a finite set of patternson Wikipedia. These are the more efficient ones to work with when searching for words in dictionary.
无论如何，您可以查看维基百科上有限模式集上的字符串搜索算法列表。在字典中搜索单词时，这些是更有效的工作。
