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import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.DoubleBuffer;
import java.nio.LongBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
public static void main(String[] args) {
long[] primes = new long[] { 1, 2, 3, 5, 7 };
File aFile = new File("C:/test/primes.txt");
FileOutputStream outputFile = null;
try {
outputFile = new FileOutputStream(aFile);
} catch (FileNotFoundException e) {
e.printStackTrace(System.err);
}
FileChannel file = outputFile.getChannel();
final int BUFFERSIZE = 100;
ByteBuffer buf = ByteBuffer.allocate(BUFFERSIZE);
DoubleBuffer doubleBuf = buf.asDoubleBuffer();
buf.position(8);
CharBuffer charBuf = buf.asCharBuffer();
for (long prime : primes) {
String primeStr = "prime = " + prime;
doubleBuf.put(0, (double) primeStr.length());
charBuf.put(primeStr);
buf.position(2 * charBuf.position() + 8);
LongBuffer longBuf = buf.asLongBuffer();
longBuf.put(prime);
buf.position(buf.position() + 8);
buf.flip();
try {
file.write(buf);
} catch (IOException e) {
e.printStackTrace(System.err);
}
buf.clear();
doubleBuf.clear();
charBuf.clear();
}
try {
System.out.println("File written is " + file.size() + "bytes.");
outputFile.close();
} catch (IOException e) {
e.printStackTrace(System.err);
}
}
}
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