![BufferedReader and BufferedWriter - 1]()
Java’s
BufferedReader
class reads text from a stream of symbols, buffering the symbols to efficiently read characters, arrays, and strings. You can pass the buffer size to the constructor as a second argument.
Constructors:
BufferedReader(Reader in) // Creates a buffered stream for reading symbols. It uses the default buffer size.
BufferedReader(Reader in, int sz) // Creates a buffered stream for reading symbols. It uses the specified buffer size.
Methods:
close() // Close the stream
mark(int readAheadLimit) // Mark the position in the stream
markSupported() // Indicates whether stream marking is supported
int read() // Read the buffer
int read(char[] cbuf, int off, int len) // Read the buffer
String readLine() // Next line
boolean ready() // Is the stream ready to read?
reset() // Reset the stream
skip(long n) // Skip characters
Here's an example of using the BufferedReader
and BufferedWriter
classes:
Reading a file:
import java.io.*;
public class ReadFile {
public static void main(String[] args) {
try {
File file = new File("file.txt");
FileReader fileReader = new FileReader(file); // A stream that connects to the text file
BufferedReader bufferedReader = new BufferedReader(fileReader); // Connect the FileReader to the BufferedReader
String line;
while((line = bufferedReader.readLine()) != null) {
System.out.println(line); // Display the file's contents on the screen, one line at a time
}
bufferedReader.close(); // Close the stream
} catch (Exception e) {
e.printStackTrace();
}
}
}
Java's
BufferedWriter
class writes text to an output character stream, buffering the characters in order to efficiently write characters, arrays, and strings. You can pass the buffer size to the constructor as a second argument.
Constructors:
BufferedWriter(Writer out) // Create a buffered output character stream that uses the default buffer size.
BufferedWriter(Writer out, int sz) // Creates a buffered character output stream that uses a buffer with the specified size.
Methods:
close() // Close the stream
flush() // Send the data from the buffer to the Writer
newLine() // Move to a new line
write(char[] cbuf, int off, int len) // Write to the buffer
write(int c) // Write to the buffer
write(String s, int off, int len) // Write to the buffer
![BufferedReader and BufferedWriter - 3]()
Here's an example of using Java's BufferedReader
and BufferedWriter
classes:
Writing to a file:
import java.io.*;
public class WriteFile {
public static void main(String[] args) {
String[] list = {"one", "two", "three", "fo"};
try {
File file = new File("file.txt");
FileWriter fileReader = new FileWriter(file); // A stream that connects to the text file
BufferedWriter bufferedWriter = new BufferedWriter(fileReader); // Connect the FileWriter to the BufferedWriter
for (String s : list) {
bufferedWriter.write(s + "\n");
}
bufferedWriter.close (); // Close the stream
} catch (Exception e) {
e.printStackTrace();
}
}
}
FileWriter
immediately writes data to disk. Every time we access it, the buffer wrapped around it speeds up our application. The buffer will write data internally, and then later write large chunks of files to disk.
We read data from the console and write it to a file:
import java.io.*;
class ConsoleRead {
public static void main(String[] args) {
try {
File file = new File("file.txt");
InputStreamReader inputStreamReader = new InputStreamReader(System.in); // A stream for reading from the console
BufferedReader bufferedReader = new BufferedReader(inputStreamReader); // Connect InputStreamReader to a BufferedReader
FileWriter fileReader = new FileWriter(file); // A stream that connects to the text file
BufferedWriter bufferedWriter = new BufferedWriter(fileReader); // Connect the FileWriter to the BufferedWriter
String line;
while(!(line = bufferedReader.readLine()).equals("exit")) {
bufferedWriter.write(line);
}
bufferedReader.close(); // Close the stream
bufferedWriter.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
John Selawsky
Senior Java Developer and Tutor at LearningTree
A senior Java developer and Java tutor at Learning Tree International programming courses. Sometimes I write some stupid programmi ...
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