Perform refactoring: proper names, avoid extra new, extract constants etc

Author: andrei-punko

sound-recorder-n-spectrum-analyzer/src/main/java/by/andd3dfx/capturesound/ShowRealTimeSpectrumApp.java

@@ -12,15 +12,18 @@
 import javax.sound.sampled.LineUnavailableException;
 import javax.sound.sampled.TargetDataLine;
 import java.io.ByteArrayOutputStream;
+import java.util.Arrays;
 
 /**
  * Application that shows real-time spectrum
  */
 public class ShowRealTimeSpectrumApp {
 
+    private final static int BUCKETS_AMOUNT = 1_000;
+
     public static void main(String[] args) throws LineUnavailableException {
         FrequencyScanner frequencyScanner = new FrequencyScanner();
-        AudioFormat audioFormat = getAudioFormat();
+        AudioFormat audioFormat = buildAudioFormat();
         DataLine.Info dataLineInfo = new DataLine.Info(TargetDataLine.class, audioFormat);
 
         ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
@@ -31,6 +34,8 @@ public static void main(String[] args) throws LineUnavailableException {
         chartContainer.show();
 
         byte tempBuffer[] = new byte[10_000];
+        double[] xData = new double[BUCKETS_AMOUNT];
+        double[] yData = new double[BUCKETS_AMOUNT];
         while (true) {
             targetDataLine.start();
             int count = targetDataLine.read(tempBuffer, 0, tempBuffer.length);
@@ -45,24 +50,25 @@ public static void main(String[] args) throws LineUnavailableException {
             double[] frequencies = frequencyInfoContainer.frequencies();
             double[] magnitudes = frequencyInfoContainer.magnitudes();
 
-            int N = 1_000;
-            double[] xData = new double[N];
-            double[] yData = new double[N];
-            for (int bucketIndex = 0; bucketIndex < N; bucketIndex++) {
-                xData[bucketIndex] = frequencies[(int) ((bucketIndex + 0.5) * magnitudes.length / N)];
+            Arrays.fill(xData, 0);
+            Arrays.fill(yData, 0);
+            final int magnitudesPerBucket = magnitudes.length / BUCKETS_AMOUNT;
+            for (int bucket = 0; bucket < BUCKETS_AMOUNT; bucket++) {
+                xData[bucket] = frequencies[(int) ((bucket + 0.5) * magnitudesPerBucket)];
 
-                for (int i = 0; i < magnitudes.length / N; i++) {
-                    yData[bucketIndex] += magnitudes[bucketIndex * magnitudes.length / N + i];
+                for (int i = 0; i < magnitudesPerBucket; i++) {
+                    yData[bucket] += magnitudes[bucket * magnitudesPerBucket + i];
                 }
             }
-            var maxFrequency = frequencyInfoContainer.maxFrequency();
 
+            var maxFrequency = frequencyInfoContainer.maxFrequency();
             String title = String.format("%1$.0f Hz", maxFrequency);
+
             chartContainer.update(xData, yData, title);
         }
     }
 
-    private static AudioFormat getAudioFormat() {
+    private static AudioFormat buildAudioFormat() {
         return new AudioFormat(44_100.0F, 16, 1, true, false);
     }
 

sound-recorder-n-spectrum-analyzer/src/main/java/by/andd3dfx/capturesound/fft/FrequencyScanner.java

@@ -13,8 +13,6 @@
  */
 public class FrequencyScanner {
 
-    private double[] windowFilter;
-
     public FrequencyInfoContainer detectFrequency(byte[] audioData, int sampleRate) {
         short[] sampleData = new short[audioData.length / 2];
         ByteBuffer.wrap(audioData).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().get(sampleData);
@@ -62,24 +60,7 @@ public FrequencyInfoContainer extractFrequencyInfo(short[] sampleData, int sampl
     }
 
     /**
-     * build a Hamming window filter for samples of a given size
-     * <p>
-     * See http://www.labbookpages.co.uk/audio/firWindowing.html#windows
-     *
-     * @param size the sample size for which the filter will be created
-     */
-    private void buildHammingWindow(int size) {
-        if (windowFilter != null && windowFilter.length == size) {
-            return;
-        }
-        windowFilter = new double[size];
-        for (int i = 0; i < size; ++i) {
-            windowFilter[i] = .54 - .46 * Math.cos(2 * Math.PI * i / (size - 1.0));
-        }
-    }
-
-    /**
-     * apply a Hamming window filter to raw input data
+     * Apply a Hamming window filter to raw input data
      *
      * @param input an array containing unfiltered input data
      * @return a double array containing the filtered data
@@ -88,10 +69,25 @@ private double[] applyWindow(short[] input) {
         var len = input.length;
         double[] res = new double[len];
 
-        buildHammingWindow(len);
+        double[] windowFilter = buildHammingWindow(len);
         for (int i = 0; i < len; ++i) {
             res[i] = (double) input[i] * windowFilter[i];
         }
         return res;
     }
+
+    /**
+     * Build a Hamming window filter for samples of a given size
+     * <p>
+     * See <a href="http://www.labbookpages.co.uk/audio/firWindowing.html#windows">link</a> for details
+     *
+     * @param size the sample size for which the filter will be created
+     */
+    private double[] buildHammingWindow(int size) {
+        var res = new double[size];
+        for (int i = 0; i < size; ++i) {
+            res[i] = 0.54 - 0.46 * Math.cos(2 * Math.PI * i / (size - 1.0));
+        }
+        return res;
+    }
 }