只过滤大型txt文件中的可读字符

Question

我有一个大的. txt文件，里面充满了可读和不可读的字符。我试图创建一个Java的程序，它可以创建一个新的. txt文件，只有以前的. txt文件中的可读字符。请帮我做这件事。任何代码都将不胜感激。我是新来Java。

Answer 1

如果可读u指的是从“a”到“z”以及从“1”到“9”的所有字符，则可以使用正则表达式过滤掉这些字符，如下所示：

public static String removeSpecialCharacters(String sentence) {
    //StringBuilder container to store all the data in
    StringBuilder stringB = new StringBuilder();
    //loop trough all the characters from the sentence
    for (char c : sentence.toCharArray()) {
        //only store characters that are equal to the below values
        if ((c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || c == ' ' ) {
            stringB.append(c);
        }
    }
    return stringB.toString().toLowerCase();
}

您可以使用返回类型（字符串）追加到新的。txt容器。比方说，对于通过removeSpecialCharacters（）方法从旧文件循环中读取的每一行，使用返回值并将其附加到新文件循环中。txt文件。

如果我们在读/写文件上读取标准的java文档，我们可以编译以下代码：

import static java.nio.file.StandardOpenOption.*;
import java.nio.file.*;
import java.io.*;


public class Main {

    public static void main(String[] args) {

        readFromFile();

    }

    private static void writeToFile(String line) {
        // Convert the string to a
        // byte array.
        byte data[] = removeSpecialCharacters(line).getBytes();
        Path p = Paths.get("/home/user/Desktop/outFile.txt");

        try (OutputStream out = new BufferedOutputStream(Files.newOutputStream(p, CREATE, APPEND))) {
            out.write(data, 0, data.length);
        } catch (IOException x) {
            System.err.println(x);
        }    
    }

    private static void readFromFile() {
        Path file = Paths.get("/home/user/Desktop/inFile.txt");
        try (InputStream in = Files.newInputStream(file);
            BufferedReader reader =
              new BufferedReader(new InputStreamReader(in))) {
            String line = null;
            while ((line = reader.readLine()) != null) {
                writeToFile(line +"\n");
            }
        } catch (IOException x) {
            System.err.println(x);
        }
    }

    public static String removeSpecialCharacters(String sentence) {
        //StringBuilder container to store all the data in
        StringBuilder stringB = new StringBuilder();
        //loop trough all the characters from the sentence
        for (char c : sentence.toCharArray()) {
            //only store characters that are equal to the below values
            if ((c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || c == ' ' ) {
                stringB.append(c);
            }
        }
        return stringB.toString().toLowerCase();
    }
}