Writing Files - Beginning Java 2 SDK - page 420

long number = 5; // Next integer to be tested
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.txt");
FileOutputStream outputFile = null;
try {
outputFile = new FileOutputStream(aFile);
} catch (FileNotFoundException e) {
e.printStackTrace(System.err);
System.exit(1);
}
FileChannel file = outputFile.getChannel();
// Array of buffer references
ByteBuffer[] buffers = new ByteBuffer[3];
buffers[0] = ByteBuffer.allocate(8); // To hold a double value
buffers[2] = ByteBuffer.allocate(8); // To hold a long value
String primeStr = null;
for (int primesWritten = 0; primesWritten < primes.length;
primesWritten++) {
primeStr = "prime = " + primes[primesWritten];
buffers[0].putDouble((double) primeStr.length()).flip();
buffers[1] = ByteBuffer.allocate(primeStr.length());
buffers[1].put(primeStr.getBytes()).flip();
buffers[2].putLong(primes[primesWritten]).flip();
try {
file.write(buffers);
} catch (IOException e) {
e.printStackTrace(System.err);
System.exit(1);
}
buffers[0].clear();
buffers[2].clear();
}
try {
System.out.println("File written is " + file.size() + " bytes.");