Fastest way to write to file?

Question

Make sure you allocate a large enough buffer:

BufferedWriter out = new BufferedWriter(new FileWriter(file), 32768);

What sort of OS are you running on? That can make a big difference too. However, taking a minute to write out a file of less-than-enormous size sounds like a system problem. On Linux or other *ix systems, you can use things like strace to see if the JVM is making lots of unnecessary system calls. (A very long time ago, Java I/O was pretty dumb and would make insane numbers of low-level write() system calls if you weren't careful, but when I say "a long time ago" I mean 1998 or so.)

edit — note that the situation of a Java program writing a simple file in a simple way, and yet being really slow, is an inherently odd one. Can you tell if the CPU is heavily loaded while the file is being written? It shouldn't be; there should be almost no CPU load from such a thing.

A simple test for you

char[] chars = new char[100*1024*1024];
Arrays.fill(chars, 'A');
String text = new String(chars);
long start = System.nanoTime();
BufferedWriter bw = new BufferedWriter(new FileWriter("/tmp/a.txt"));
bw.write(text);
bw.close();
long time = System.nanoTime() - start;
System.out.println("Wrote " + chars.length*1000L/time+" MB/s.");

Prints

Wrote 135 MB/s.

You could look into Java's NIO capabilities. It may support what you want to do.

Java NIO FileChannel versus FileOutputstream performance / usefulness

Try using memory mapped files:

FileChannel rwChannel = new RandomAccessFile("textfile.txt", "rw").getChannel();
ByteBuffer wrBuf = rwChannel.map(FileChannel.MapMode.READ_WRITE, 0, textToSave.length());

wrBuf.put(textToSave.getBytes());

rwChannel.close();