Writing Files - Beginning Java 2 SDK - page 410

// Count of primes found - up to now, which is also the array index
int count = 2;
// Next integer to be tested
long number = 5;
outer:
for (; count < primesRequired; number += 2) {
// The maximum divisor we need to try is square root of number
long limit = (long) Math.ceil(Math.sqrt((double) number));
// Divide by all the primes we have up to limit
for (int i = 1; i < count && primes[i] <= limit; i++)
if (number % primes[i] == 0) // Is it an exact divisor?
continue outer; // yes, try the next number
primes[count++] = number; // We got one!
}
File aFile = new File("C:/Beg Java Stuff/primes.bin");
FileOutputStream outputFile = null;
try {
outputFile = new FileOutputStream(aFile); // Create the file stream
} catch (FileNotFoundException e) {
e.printStackTrace(System.err);
System.exit(1);
}
FileChannel file =
// Get the channel from the stream
outputFile.getChannel();
final int BUFFERSIZE = 100; // Byte buffer size
ByteBuffer buf = ByteBuffer.allocate(BUFFERSIZE);
LongBuffer longBuf = buf.asLongBuffer(); // View buffer for type long
// Count of primes written to file
int primesWritten = 0;
while (primesWritten < primes.length) {
longBuf.put(primes, // Array to be written
primesWritten, // Index of 1st element to be written
Math.min(longBuf.capacity(),
primes.length - primesWritten)); // Element count
buf.limit(8 * longBuf.position());
try {
file.write(buf);
primesWritten += longBuf.position();
} catch (IOException e) {
e.printStackTrace(System.err);
System.exit(1);
}
longBuf.clear();
buf.clear();
}