In Java I/O operations, file reading and writing are common and frequent tasks. Especially for large files or programs that require frequent access to files, how to improve I/O performance has become an important issue. In these cases, it is particularly important to use a buffered stream. Today, let’s learn about what buffer stream is, why it improves I/O performance, and how to use it in real development.
What is a buffered stream?
Buffered streams are a class of streams in Java I/O packages, which are usually used with other byte streams or character streams to increase the efficiency of I/O operations. Compared with ordinary input and output streams, buffered streams reduce the number of actual read and write operations by using internal buffers (memory areas), thereby increasing the speed of file reading and writing.
There are two main types of buffered streams in Java:
-
Byte buffered stream：
BufferedInputStreamandBufferedOutputStream, mainly deals with byte streams. -
Character buffer stream：
BufferedReaderandBufferedWriter, mainly deals with character streams.
These buffer streams do not read or write files directly, but batch process data by creating a buffer in memory, reducing the actual number of I/O operations.
How to improve I/O performance by buffered streams?
I/O operations are essentially a time-consuming process, especially in file operations, where data is required to be read from disk to memory or write data in memory to disk each time. Each I/O operation involves the interaction between the operating system and the hardware, so it is a very slow process.
The buffer stream is completed at one time by creating a buffer in memory, reading or writing operations of multiple data. The working principle of buffered streams is roughly like this:
- Buffer: Buffered streams will create a buffer (usually a byte array) in memory. When reading data, the buffer will read a certain amount of data into memory from a file or other input source at once.
- Batch read/write: The subsequent read or write operations do not directly operate on the file, but obtain or write data from the buffer. This means that the program can avoid frequent I/O operations, thereby improving performance.
- Reduce I/O times: Buffered stream effectively reduces the number of accesses to the hard disk. Because the operating system usually pre-reads a certain data block when reading data, and the buffered stream takes advantage of this feature to reduce the number of I/O times by reading a large amount of data at one time.
In general, buffer streams pass in memory cache mechanisms, reducing actual disk operations every read and write, thereby improving I/O efficiency, especially when processing large files or requiring frequent read and write files, the performance improvement is more obvious.
Common buffer flow classes and usage methods
Byte buffered stream:BufferedInputStreamandBufferedOutputStream
BufferedInputStreamandBufferedOutputStreamMainly used for processing byte streams. They provide buffers for both input and output streams, reducing I/O overhead for each read and write operation.
Example code: Use of byte buffered streams
import .*;
public class BufferedStreamExample {
public static void main(String[] args) {
try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(""));
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(""))) {
int byteData;
while ((byteData = ()) != -1) {
(byteData);
}
("File copy is complete!");
} catch (IOException e) {
();
}
}
}In this example,BufferedInputStreamfromread data from the file, andBufferedOutputStreamWrite data todocument. Because of the use of buffered streams, the program does not need to read or write one byte at a time, but batch processing is performed at one time.
Character buffer stream:BufferedReaderandBufferedWriter
BufferedReaderandBufferedWriterClasses are buffered stream versions of character streams. They are particularly suitable for processing character data and can more efficiently read and write text files.
Example code: Use of character buffer streams
import .*;
public class BufferedReaderWriterExample {
public static void main(String[] args) {
try (BufferedReader br = new BufferedReader(new FileReader(""));
BufferedWriter bw = new BufferedWriter(new FileWriter(""))) {
String line;
while ((line = ()) != null) {
(line);
(); // Write newline characters }
("File copy is complete!");
} catch (IOException e) {
();
}
}
}In this example,BufferedReaderfromread text line by line, andBufferedWriterWrite text tomiddle. Through the use of buffered streams, programs can batch read and write data, avoiding frequent I/O operations.
Summarize
Buffered streams are an important tool for improving performance in Java I/O operations. By using buffers, the buffered stream reduces the number of interactions with the hard disk, making I/O operation more efficient. In scenarios where large amounts of data are processed or files are frequently accessed, buffered streams can significantly improve program performance. Whether it is a byte stream or a character stream, buffered streams provide a simple and effective solution. In actual development, it is recommended to use buffered streams to perform file operations as much as possible, especially when dealing with large files, which can bring significant performance improvements.
Overall, the use of buffered streams is a must-have skill for every Java developer, which can make our programs more efficient and elegant when handling file I/O.
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