Interview question

What is Character Encoding in file I/O? How do you handle different charsets? File I/O में Character Encoding क्या है? Different charsets कैसे handle करते हैं?

Answer

Character encoding specifies how characters are represented as bytes. Different encodings (UTF-8, UTF-16, ASCII, ISO-8859-1) store characters differently. Incorrect encoding causes garbled text.

import java.io.*;
import java.nio.charset.StandardCharsets;

public class CharsetDemo {
    public static void main(String[] args) {
        String text = 'Hello, 你好, नमस्ते';
        
        // Writing with specific charset
        try (FileWriter fw = new FileWriter('utf8.txt', 
                StandardCharsets.UTF_8)) {
            fw.write(text);
            System.out.println('UTF-8 file written');
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        // Reading with specific charset
        try (FileReader fr = new FileReader('utf8.txt', 
                StandardCharsets.UTF_8)) {
            int ch;
            while ((ch = fr.read()) != -1) {
                System.out.print((char) ch);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        // Using InputStreamReader for charset control
        try (InputStreamReader isr = new InputStreamReader(
                new FileInputStream('file.txt'), 
                StandardCharsets.UTF_8)) {
            BufferedReader br = new BufferedReader(isr);
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        // Using OutputStreamWriter for charset control
        try (OutputStreamWriter osw = new OutputStreamWriter(
                new FileOutputStream('output.txt'),
                StandardCharsets.UTF_8)) {
            osw.write('Multilingual text: Hello, 世界, мир');
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

// Common charsets
// UTF-8: Variable-length encoding (1-4 bytes per character)
// UTF-16: Fixed 2-byte encoding
// ASCII: 7-bit encoding (English only)
// ISO-8859-1: European characters
// GBK: Chinese characters

// Detect encoding
public class EncodingDetection {
    public static String detectEncoding(File file) {
        // Using Apache Commons IO or ICU4J libraries
        // Or detect BOM (Byte Order Mark)
        return 'UTF-8';
    }
}

Character Encoding:

1. UTF-8 (Most common):
   - Variable-length (1-4 bytes)
   - Supports all languages
   - Backward-compatible with ASCII

2. UTF-16: Fixed 2-byte
3. ASCII: English only (7-bit)
4. ISO-8859-1: European chars

Handling Different Charsets:

FileWriter/FileReader (Java 11+):
try (FileWriter fw = new FileWriter('file.txt',
        StandardCharsets.UTF_8)) {
    fw.write(text);
}

InputStreamReader (older Java):
try (InputStreamReader isr = new InputStreamReader(
        new FileInputStream('file.txt'),
        StandardCharsets.UTF_8)) {
    // Read with specific charset
}

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