Add VAD demo for Java API (#928)

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

@@ -0,0 +1,78 @@
+// Copyright 2024 Xiaomi Corporation
+
+package com.k2fsa.sherpa.onnx;
+
+public class Vad {
+    static {
+        System.loadLibrary("sherpa-onnx-jni");
+    }
+
+    private long ptr = 0;
+
+    public Vad(VadModelConfig config) {
+        ptr = newFromFile(config);
+    }
+
+    @Override
+    protected void finalize() throws Throwable {
+        release();
+    }
+
+    public void release() {
+        if (this.ptr == 0) {
+            return;
+        }
+        delete(this.ptr);
+        this.ptr = 0;
+    }
+
+    public void acceptWaveform(float[] samples) {
+        acceptWaveform(this.ptr, samples);
+    }
+
+    public boolean empty() {
+        return empty(this.ptr);
+    }
+
+    public void pop() {
+        pop(this.ptr);
+    }
+
+    public void clear() {
+        clear(this.ptr);
+    }
+
+    public void reset() {
+        reset(this.ptr);
+    }
+
+    public SpeechSegment front() {
+        Object[] arr = front(this.ptr);
+        int start = (int) arr[0];
+        float[] samples = (float[]) arr[1];
+
+        return new SpeechSegment(start, samples);
+    }
+
+    public boolean isSpeechDetected() {
+        return isSpeechDetected(this.ptr);
+    }
+
+    private native void delete(long ptr);
+
+    private native long newFromFile(VadModelConfig config);
+
+    private native void acceptWaveform(long ptr, float[] samples);
+
+    private native boolean empty(long ptr);
+
+    private native void pop(long ptr);
+
+    private native void clear(long ptr);
+
+    private native Object[] front(long ptr);
+
+    private native boolean isSpeechDetected(long ptr);
+
+    private native void reset(long ptr);
+}