java nio 无法写入文件，旧式文件可以工作。怎么了？`

Question

下面的MWE展示了我对如何使用nio编写文件的理解。但是打开文件失败。为了证明该目录没有任何问题，在同一项目、同一目录中写入了一个老式文件。 nio代码有什么问题？

错误:线程“main”java.nio.file.NoSuchFileException 中出现异常:test.dat。请注意，该选项设置为 CREATE，它应该写入现有文件或创建新文件!

import java.io.*;
import java.nio.*;
import java.nio.file.*;
import java.nio.channels.*;

public class FastWritenio {
    public static void writeUsingPrintWriter() throws IOException {
        PrintWriter pw = new PrintWriter(new FileWriter("test.txt"));
        pw.print("testing");
        pw.close();
    }
    public static void writeUsingnio(int numTrials, int bufferSize, int putsPer) throws IOException {
        String filename = "test.dat";
        java.nio.file.Path filePath = Paths.get(filename);
        WritableByteChannel channel = Files.newByteChannel(filePath, StandardOpenOption.CREATE);
        ByteBuffer buf = ByteBuffer.allocate(bufferSize);
        for (int t = 0; t < numTrials; ++t) {
            for (int i = 0; i < putsPer; i ++) {
                buf.putInt(i);
            }
            buf.flip(); // stop modifying buffer so it can be written to disk
            channel.write(buf);  // Write your buffer's data.
        }
        channel.close();
    }
    public static void main(String[] args) throws IOException {
        writeUsingPrintWriter();
        writeUsingnio(16, 8*1024, 1024);
    }
}

Answer 1

引自documentation :

Both newByteChannel methods enable you to specify a list of OpenOption options. The same open options used by the newOutputStream methods are supported, in addition to one more option: READ is required because the SeekableByteChannel supports both reading and writing.

Specifying READ opens the channel for reading. Specifying WRITE or APPEND opens the channel for writing. If none of these options is specified, the channel is opened for reading.

您的OpenOptions 不足。在示例中设置 WritableByteChannel channel = Files.newByteChannel(filePath, StandardOpenOption.CREATE, StandardOpenOption.APPEND); 会在 Windows 上创建文件，但最终会出现 BufferOverflow。