Java में FileReader और FileWriter
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FileReader reader = new FileReader("file_name");
FileWriter writer = new FileWriter("file_name");
writer.write("text");
writer.close();Writing Characters with FileWriter
FileWriter एक file में character data लिखता है, Java की internal char/String data को लिखते समय अपने आप platform के default text encoding में convert करते हुए।
उदाहरण: Writing Characters with FileWriter
// Import java.io.FileWriter so it can be used by its short name
import java.io.FileWriter;
// Import java.io.IOException so it can be used by its short name
import java.io.IOException;
// Define the class Main
public class Main {
// Program entry point: the JVM starts running here
public static void main(String[] args) throws IOException {
// Create a new FileWriter object and store it in writer
FileWriter writer = new FileWriter("notes.txt");
writer.write("Hello");
writer.close();
// Print a line to the console
System.out.println("Written");
}
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Reading Characters with FileReader
FileReader उसी तरह एक file से character data वापस पढ़ता है, पढ़ते समय डिस्क पर bytes को Java char values में convert करते हुए — text को round-tripping करने के लिए naturally FileWriter के साथ जोड़ा जाता है।
उदाहरण: Reading Characters with FileReader
// Import java.io.FileWriter so it can be used by its short name
import java.io.FileWriter;
// Import java.io.FileReader so it can be used by its short name
import java.io.FileReader;
import java.io.IOException;
// Define the class Main
public class Main {
// Program entry point: the JVM starts running here
public static void main(String[] args) throws IOException {
// Create a new FileWriter object and store it in writer
FileWriter writer = new FileWriter("notes.txt");
writer.write("Hi");
writer.close();
// Create a new FileReader object and store it in reader
FileReader reader = new FileReader("notes.txt");
int c;
// Repeat while (c = reader.read()) != -1 is true
while ((c = reader.read()) != -1) {
// Print to the console without a newline
System.out.print((char) c);
}
reader.close();
}
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Try-With-Resources cleanup
Try-with-resources उपयोग करना (try (FileWriter fw = new FileWriter(...)) {...}) गारंटी देता है कि file block exit होने पर अपने आप बंद हो, भले ही बीच में एक exception throw हो।
उदाहरण: Try-With-Resources cleanup
import java.io.FileWriter;
import java.io.IOException;
public class Main {
public static void main(String[] args) throws IOException {
try (FileWriter writer = new FileWriter("notes.txt")) { // auto-closed on exit
writer.write("Hello");
}
System.out.println("Closed automatically");
}
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File Handling Safety
File operations को हमेशा proper exception handling और resource closing में wrap करें — एक unclosed file handle resources leak कर सकता है, और एक program जो mid-write crash हो जाए वह एक file को corrupted, half-written state में छोड़ सकता है।
उदाहरण: File Handling Safety
// Import java.io.FileWriter so it can be used by its short name
import java.io.FileWriter;
// Import java.io.IOException so it can be used by its short name
import java.io.IOException;
// Define the class Main
public class Main {
// Program entry point: the JVM starts running here
public static void main(String[] args) {
// Try code that might throw an exception
try (FileWriter writer = new FileWriter("notes.txt")) {
writer.write("Hello");
// Handle IOException if it was thrown
} catch (IOException e) {
// Print a line to the console
System.out.println("Handled safely: " + e.getMessage());
}
}
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Dynamic Text Manipulation
चूंकि FileWriter default रूप से character-by-character लिखता है, इसे एक loop के साथ combine करना जो strings build और rewrite करता है किसी file की text content को fly पर transform करने का एक natural तरीका है।
उदाहरण: Dynamic Text Manipulation
// Import java.io.FileWriter so it can be used by its short name
import java.io.FileWriter;
// Import java.io.IOException so it can be used by its short name
import java.io.IOException;
// Define the class Main
public class Main {
// Program entry point: the JVM starts running here
public static void main(String[] args) throws IOException {
// Create a new StringBuilder object and store it in content
StringBuilder content = new StringBuilder();
// Loop: repeat while the condition holds
for (int i = 1; i <= 3; i++) {
content.append("Line ").append(i).append("\n");
}
// Try code that might throw an exception
try (FileWriter writer = new FileWriter("notes.txt")) {
writer.write(content.toString());
}
// Print a line to the console
System.out.println("Written dynamically");
}
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- बिना append mode के
FileWriterउपयोग करना, जो मौजूदा text overwrite करता है। - Writer बंद करना भूल जाना, इसलिए text save नहीं हो सकता।
- Binary files के लिए
FileReaderउपयोग करना, जो data corrupt करता है।
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