migrate ThreadPoolBridge to interface pattern

Author: yaauie

libs/logstash-bridge/src/main/java/org/elasticsearch/logstashbridge/threadpool/ThreadPoolBridge.java

@@ -19,25 +19,38 @@
 /**
  * An external bridge for {@link ThreadPool}
  */
-public class ThreadPoolBridge extends StableBridgeAPI.ProxyInternal<ThreadPool> {
+public interface ThreadPoolBridge extends StableBridgeAPI<ThreadPool> {
 
-    public ThreadPoolBridge(final SettingsBridge settingsBridge) {
-        this(new ThreadPool(settingsBridge.toInternal(), MeterRegistry.NOOP, new DefaultBuiltInExecutorBuilders()));
-    }
+    long relativeTimeInMillis();
 
-    public ThreadPoolBridge(final ThreadPool delegate) {
-        super(delegate);
-    }
+    long absoluteTimeInMillis();
 
-    public static boolean terminate(final ThreadPoolBridge pool, final long timeout, final TimeUnit timeUnit) {
-        return ThreadPool.terminate(pool.toInternal(), timeout, timeUnit);
-    }
+    boolean terminate(long timeout, TimeUnit timeUnit);
 
-    public long relativeTimeInMillis() {
-        return internalDelegate.relativeTimeInMillis();
+    static ThreadPoolBridge create(final SettingsBridge bridgedSettings) {
+        final ThreadPool internal = new ThreadPool(bridgedSettings.toInternal(), MeterRegistry.NOOP, new DefaultBuiltInExecutorBuilders());
+        return new ProxyInternal(internal);
     }
 
-    public long absoluteTimeInMillis() {
-        return internalDelegate.absoluteTimeInMillis();
+    class ProxyInternal extends StableBridgeAPI.ProxyInternal<ThreadPool> implements ThreadPoolBridge {
+
+        ProxyInternal(final ThreadPool delegate) {
+            super(delegate);
+        }
+
+        @Override
+        public long relativeTimeInMillis() {
+            return internalDelegate.relativeTimeInMillis();
+        }
+
+        @Override
+        public long absoluteTimeInMillis() {
+            return internalDelegate.absoluteTimeInMillis();
+        }
+
+        @Override
+        public boolean terminate(final long timeout, final TimeUnit timeUnit) {
+            return ThreadPool.terminate(internalDelegate, timeout, timeUnit);
+        }
     }
 }