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import java.io.File;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
public class Main {
public static void main(String[] args) throws Exception {
File aFile = new File("C:/test.bin");
RandomAccessFile ioFile = new RandomAccessFile(aFile, " rw");
FileChannel ioChannel = ioFile.getChannel();
final int PRIMESREQUIRED = 10;
long[] primes = new long[PRIMESREQUIRED];
int index = 0;
final long REPLACEMENT = 999999L;
final int PRIMECOUNT = (int) ioChannel.size() / 8;
MappedByteBuffer buf = ioChannel.map(FileChannel.MapMode.READ_WRITE, 0L, ioChannel.size())
.load();
ioChannel.close();
for (int i = 0; i < PRIMESREQUIRED; i++) {
index = 8 * (int) (PRIMECOUNT * Math.random());
primes[i] = buf.getLong(index);
buf.putLong(index, REPLACEMENT);
}
for (long prime : primes) {
System.out.printf("%12d", prime);
}
ioFile.close();
}
}
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