ByteBuffer: put(byte b)
import java.io.FileOutputStream; import java.io.IOException; import java.nio.ByteBuffer; import java.nio.channels.FileChannel; public class MainClass { public static void main(String args[]) { FileOutputStream fileOutputStream; FileChannel fileChannel; ByteBuffer byteBuffer; try { fileOutputStream = new FileOutputStream("test.txt"); fileChannel = fileOutputStream.getChannel(); byteBuffer = ByteBuffer.allocateDirect(26); for (int i = 0; i < 26; i++) byteBuffer.put((byte) ('A' + i)); byteBuffer.rewind(); fileChannel.write(byteBuffer); fileChannel.close(); fileOutputStream.close(); } catch (IOException exc) { System.out.println(exc); } } }