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处理大文件时,Java IO 流的一些技巧可以帮助提高性能和减少内存占用。以下是一些建议:
InputStream inputStream = new BufferedInputStream(new FileInputStream("largeFile.txt"));
OutputStream outputStream = new BufferedOutputStream(new FileOutputStream("largeFile.txt"));
Path path = Paths.get("largeFile.txt");
try (FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.READ)) {
ByteBuffer buffer = ByteBuffer.allocateDirect(1024 * 1024); // 1MB buffer
while (fileChannel.read(buffer) != -1) {
buffer.flip();
// Process the buffer
buffer.compact();
}
} catch (IOException e) {
e.printStackTrace();
}
Path path = Paths.get("largeFile.txt");
try (FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.READ)) {
MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, fileChannel.size());
// Process the mappedByteBuffer
} catch (IOException e) {
e.printStackTrace();
}
long fileSize = new File("largeFile.txt").length();
int bufferSize = 1024 * 1024; // 1MB
for (long position = 0; position < fileSize; position += bufferSize) {
long bytesToRead = Math.min(bufferSize, fileSize - position);
byte[] buffer = new byte[(int) bytesToRead];
try (FileInputStream inputStream = new FileInputStream("largeFile.txt")) {
inputStream.skip(position);
int bytesRead = inputStream.read(buffer);
// Process the buffer
} catch (IOException e) {
e.printStackTrace();
}
}
int numberOfThreads = Runtime.getRuntime().availableProcessors();
ExecutorService executorService = Executors.newFixedThreadPool(numberOfThreads);
long fileSize = new File("largeFile.txt").length();
int bufferSize = 1024 * 1024; // 1MB
for (long position = 0; position < fileSize; position += bufferSize) {
long bytesToRead = Math.min(bufferSize, fileSize - position);
byte[] buffer = new byte[(int) bytesToRead];
executorService.submit(() -> {
try (FileInputStream inputStream = new FileInputStream("largeFile.txt")) {
inputStream.skip(position);
int bytesRead = inputStream.read(buffer);
// Process the buffer
} catch (IOException e) {
e.printStackTrace();
}
});
}
executorService.shutdown();
try {
executorService.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
} catch (InterruptedException e) {
e.printStackTrace();
}
try (FileInputStream inputStream = new FileInputStream("largeFile.txt");
FileOutputStream outputStream = new FileOutputStream("largeFile.txt")) {
// Process the input and output streams
} catch (IOException e) {
e.printStackTrace();
}
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