Add VAD demo for Java API (#928)

sherpa-onnx/java-api/src/com/k2fsa/sherpa/onnx/SpeechSegment.java

@@ -0,0 +1,20 @@
+package com.k2fsa.sherpa.onnx;
+
+public class SpeechSegment {
+
+    private final int start;
+    private final float[] samples;
+
+    public SpeechSegment(int start, float[] samples) {
+        this.start = start;
+        this.samples = samples;
+    }
+
+    public int getStart() {
+        return start;
+    }
+
+    public float[] getSamples() {
+        return samples;
+    }
+}