clojure

(defn float-to-two-bytes [value]
  (let [ dblval (double value) intval (int (* dblval 32765)) ]
  (if (and (>= dblval -1 ) (<= dblval 1))
    [ (byte intval) (byte (bit-shift-right intval 8)) ])))


(defn convert-float-to-byte-array [floatseq]
   (into-array Byte/TYPE 
     (reduce conj [] 
      (mapcat #(float-to-two-bytes %) floatseq))))

java

  public byte[] convertDoubleArrayToByte(double[] incoming){
    // This function converts an array of double precision samples into their byte array counterpart.
    // as with its collegue (the convertByteArrayToDouble function) it could be used for other purposes than 
    // just working with buffers the size of the DSP buffer, so it keeps track of its own incoming and outgoing
    // array sizes.
    int numberofoutgoingbytes = incoming.length << 1; // *2
    int numberofincomingdoubles = incoming.length;
    byte[] returnValues = new byte[numberofoutgoingbytes];

    short sample_as_int;  
    
    int[] result = new int[numberofincomingdoubles];
    int byteptr = 0;
    for(int i=0;i<numberofincomingdoubles;i++){
       sample_as_int = (short)Math.round(32767.0 * incoming[i]);
     
       returnValues[byteptr] = (byte)(sample_as_int & 0xFF);
       returnValues[byteptr+1] = (byte)((sample_as_int >> 8) & 0xFF); 
       // the bitshifting trick above is much faster, but does the same as the following calculation
       //byte a = (byte)((sample_as_int/256));
       //byte b = (byte)(sample_as_int-(256*a));
       byteptr+=2;
    }
    return returnValues;
  }