1. Understanding character encoding:

1. The default encoding of String in Java is UTF-8, which can be obtained using the following statement: Charset.defaultCharset( );

2. Under the Windows operating system, the default encoding of text files is ANSI, which is GBK for Chinese Windows. For example, if we use the Notepad program to create a new text document, its default character encoding is ANSI.

3. Text text documents have four encoding options: ANSI, Unicode (including Unicode Big Endian and Unicode Little Endian), UTF-8, UTF-16

4, so we read txt files may sometimes not know their encoding format, so a program needs to be used to dynamically determine the encoding of the txt file.

ANSI : No format definition, for Chinese operating systems it is GBK or GB2312

UTF-8 : The first three bytes are: 0xE59B9E (UTF-8), 0xEFBBBF (UTF-8 inclusive BOM)

UTF-16: The first two bytes are: 0xFEFF

Unicode: The first two bytes are: 0xFFFE

For example: Unicode documents start with 0xFFFE, use The program just takes out the first few bytes and makes a judgment.

5. Correspondence between Java encoding and Text encoding:

Java reads Text files. If the encoding format does not match, garbled characters will appear. Therefore, you need to set the correct character encoding when reading text files. The encoding format of Text documents is written in the file header. In the program, the encoding format of the file needs to be parsed first. After obtaining the encoding format, reading the file in this format will avoid garbled characters.

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2. For example:

There is a text file: test.txt

Test code:

/**
 * 文件名：CharsetCodeTest.java
 * 功能描述：文件字符編碼測(cè)試
 */
 
import java.io.*;
 
public class CharsetCodeTest {
    public static void main(String[] args) throws Exception {
        String filePath = "test.txt";
        String content = readTxt(filePath);
        System.out.println(content);
    }
 
 
public static String readTxt(String path) {
        StringBuilder content = new StringBuilder("");
        try {
            String fileCharsetName = getFileCharsetName(path);
            System.out.println("文件的編碼格式為："+fileCharsetName);
 
            InputStream is = new FileInputStream(path);
            InputStreamReader isr = new InputStreamReader(is, fileCharsetName);
            BufferedReader br = new BufferedReader(isr);
 
            String str = "";
            boolean isFirst = true;
            while (null != (str = br.readLine())) {
                if (!isFirst)
                    content.append(System.lineSeparator());
                    //System.getProperty("line.separator");
                else
                    isFirst = false;
                content.append(str);
            }
            br.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.err.println("讀取文件:" + path + "失敗!");
        }
        return content.toString();
    }
 
 
    public static String getFileCharsetName(String fileName) throws IOException {
        InputStream inputStream = new FileInputStream(fileName);
        byte[] head = new byte[3];
        inputStream.read(head);
 
        String charsetName = "GBK";//或GB2312，即ANSI
        if (head[0] == -1 && head[1] == -2 ) //0xFFFE
            charsetName = "UTF-16";
        else if (head[0] == -2 && head[1] == -1 ) //0xFEFF
            charsetName = "Unicode";//包含兩種編碼格式：UCS2-Big-Endian和UCS2-Little-Endian
        else if(head[0]==-27 && head[1]==-101 && head[2] ==-98)
            charsetName = "UTF-8"; //UTF-8(不含BOM)
        else if(head[0]==-17 && head[1]==-69 && head[2] ==-65)
            charsetName = "UTF-8"; //UTF-8-BOM
 
        inputStream.close();
 
        //System.out.println(code);
        return charsetName;
    }
}

Running results:

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