java.util.Scanner用于读取具有不同字符编码的文件

2023年6月9日 231次阅读

我使用
Java来读取文件列表.其中一些具有不同的编码,ANSI而不是UTF-8. java.util.Scanner无法读取这些文件并获取空输出字符串.

我尝试了另一种方法：

                FileInputStream fis = new FileInputStream(my_file);
                BufferedReader br = new BufferedReader(new InputStreamReader(fis));
                InputStreamReader isr = new InputStreamReader(fis);
                isr.getEncoding();

我不知道如何在ANSI的情况下改变字符编码. UTF-8和ANSI文件混合在同一文件夹中.我尝试使用Apache Tika.
我得到文件编码后,我使用扫描仪,但我得到空输出.

Scanner scanner = new Scanner(my_file, detector.getCharset().toString());
line = scanner.nextLine();

最佳答案 有一个名为juniversalchardet的库,它可以帮助您猜测正确的编码.它最近更新,目前位于GitHub：

https://github.com/albfernandez/juniversalchardet

但是,没有用于检测编码的故障安全工具,因为有许多未知的事情：

>这个文件是全文还是一些PNG？
>它是以(1,…,k,…,n)位编码存储的吗？
>使用了哪种k位编码？

可以通过计算不常用的控制字符的数量来完成一些猜测.当文件包含许多控制符号时,您可能选择了错误的编码. (然后尝试下一个.)

Juniversalchardet尝试多种且更成功的方法来确定编码(甚至是中文编码).它还提供了方便的方法,可以从已选择正确编码的文件中打开阅读器：

(摘自https://github.com/albfernandez/juniversalchardet#creating-a-reader-with-correct-encoding并改编)

import org.mozilla.universalchardet.ReaderFactory;
import java.io.File;
import java.io.IOException;
import java.io.Reader;

public class TestCreateReaderFromFile {

    public static void main (String[] args) throws IOException {
        if (args.length != 1) {
            System.err.println("Usage: java TestCreateReaderFromFile FILENAME");
            System.exit(1);
        }

        Reader reader = null;
        try {
            File file = new File(args[0]);
            reader = ReaderFactory.createBufferedReader(file);

            String line;
            while((line=reader.readLine())!=null){
                System.out.println(line); //Print each line to console
            }
        }
        finally {
            if (reader != null) {
                reader.close();
            }
        }

    }

}

编辑：添加了ScannerFactory

/*
(C) Copyright 2016-2017 Alberto Fernández <infjaf@gmail.com>
Adapted by Fritz Windisch 2018-11-15
The contents of this file are subject to the Mozilla Public License Version
1.1 (the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.mozilla.org/MPL/
Software distributed under the License is distributed on an "AS IS" basis,
WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
for the specific language governing rights and limitations under the
License.
Alternatively, the contents of this file may be used under the terms of
either the GNU General Public License Version 2 or later (the "GPL"), or
the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
in which case the provisions of the GPL or the LGPL are applicable instead
of those above. If you wish to allow use of your version of this file only
under the terms of either the GPL or the LGPL, and not to allow others to
use your version of this file under the terms of the MPL, indicate your
decision by deleting the provisions above and replace them with the notice
and other provisions required by the GPL or the LGPL. If you do not delete
the provisions above, a recipient may use your version of this file under
the terms of any one of the MPL, the GPL or the LGPL.
*/

import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Objects;
import java.util.Scanner;
import org.mozilla.universalchardet.UniversalDetector;
import org.mozilla.universalchardet.UnicodeBOMInputStream;

/**
 * Create a scanner from a file with correct encoding
 */
public final class ScannerFactory {

    private ScannerFactory() {
        throw new AssertionError("No instances allowed");
    }
    /**
     * Create a scanner from a file with correct encoding
     * @param file The file to read from
     * @param defaultCharset defaultCharset to use if can't be determined
     * @return Scanner for the file with the correct encoding
     * @throws java.io.IOException if some I/O error ocurrs
     */

    public static Scanner createScanner(File file, Charset defaultCharset) throws IOException {
        Charset cs = Objects.requireNonNull(defaultCharset, "defaultCharset must be not null");
        String detectedEncoding = UniversalDetector.detectCharset(file);
        if (detectedEncoding != null) {
            cs = Charset.forName(detectedEncoding);
        }
        if (!cs.toString().contains("UTF")) {
            return new Scanner(file, cs.name());
        }
        Path path = file.toPath();
        return new Scanner(new UnicodeBOMInputStream(new BufferedInputStream(Files.newInputStream(path))), cs.name());
    }
    /**
     * Create a scanner from a file with correct encoding. If charset cannot be determined,
     * it uses the system default charset.
     * @param file The file to read from
     * @return Scanner for the file with the correct encoding
     * @throws java.io.IOException if some I/O error ocurrs
     */
    public static Scanner createScanner(File file) throws IOException {
        return createScanner(file, Charset.defaultCharset());
    }
}
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