[api] Replace double-check singlton with lazy initialization

deepjavalibrary · Oct 30, 2023 · 75b8839 · 75b8839
1 parent 85d9e85
commit 75b8839
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Showing 9 changed files with 45 additions and 72 deletions.
diff --git a/engines/ml/lightgbm/src/main/java/ai/djl/ml/lightgbm/LgbmEngineProvider.java b/engines/ml/lightgbm/src/main/java/ai/djl/ml/lightgbm/LgbmEngineProvider.java
@@ -18,8 +18,6 @@
 /** {@code LgbmEngineProvider} is the LightGBM implementation of {@link EngineProvider}. */
 public class LgbmEngineProvider implements EngineProvider {
 
-    private static volatile Engine engine; // NOPMD
-
     /** {@inheritDoc} */
     @Override
     public String getEngineName() {
@@ -35,11 +33,10 @@ public int getEngineRank() {
     /** {@inheritDoc} */
     @Override
     public Engine getEngine() {
-        if (engine == null) {
-            synchronized (LgbmEngineProvider.class) {
-                engine = LgbmEngine.newInstance();
-            }
-        }
-        return engine;
+        return InstanceHolder.INSTANCE;
+    }
+
+    private static class InstanceHolder {
+        static final Engine INSTANCE = LgbmEngine.newInstance();
     }
 }
diff --git a/engines/ml/xgboost/src/main/java/ai/djl/ml/xgboost/XgbEngineProvider.java b/engines/ml/xgboost/src/main/java/ai/djl/ml/xgboost/XgbEngineProvider.java
@@ -18,8 +18,6 @@
 /** {@code XgbEngineProvider} is the XGBoost implementation of {@link EngineProvider}. */
 public class XgbEngineProvider implements EngineProvider {
 
-    private static volatile Engine engine; // NOPMD
-
     /** {@inheritDoc} */
     @Override
     public String getEngineName() {
@@ -35,11 +33,10 @@ public int getEngineRank() {
     /** {@inheritDoc} */
     @Override
     public Engine getEngine() {
-        if (engine == null) {
-            synchronized (XgbEngineProvider.class) {
-                engine = XgbEngine.newInstance();
-            }
-        }
-        return engine;
+        return InstanceHolder.INSTANCE;
+    }
+
+    private static class InstanceHolder {
+        static final Engine INSTANCE = XgbEngine.newInstance();
     }
 }
diff --git a/engines/mxnet/mxnet-engine/src/main/java/ai/djl/mxnet/engine/MxEngineProvider.java b/engines/mxnet/mxnet-engine/src/main/java/ai/djl/mxnet/engine/MxEngineProvider.java
@@ -18,8 +18,6 @@
 /** {@code MxEngineProvider} is the MXNet implementation of {@link EngineProvider}. */
 public class MxEngineProvider implements EngineProvider {
 
-    private static volatile Engine engine; // NOPMD
-
     /** {@inheritDoc} */
     @Override
     public String getEngineName() {
@@ -35,11 +33,10 @@ public int getEngineRank() {
     /** {@inheritDoc} */
     @Override
     public Engine getEngine() {
-        if (engine == null) {
-            synchronized (MxEngineProvider.class) {
-                engine = MxEngine.newInstance();
-            }
-        }
-        return engine;
+        return InstanceHolder.INSTANCE;
+    }
+
+    private static class InstanceHolder {
+        static final Engine INSTANCE = MxEngine.newInstance();
     }
 }
diff --git a/...runtime/onnxruntime-engine/src/main/java/ai/djl/onnxruntime/engine/OrtEngineProvider.java b/...runtime/onnxruntime-engine/src/main/java/ai/djl/onnxruntime/engine/OrtEngineProvider.java
@@ -18,8 +18,6 @@
 /** {@code OrtEngineProvider} is the ONNX Runtime implementation of {@link EngineProvider}. */
 public class OrtEngineProvider implements EngineProvider {
 
-    private static volatile Engine engine; // NOPMD
-
     /** {@inheritDoc} */
     @Override
     public String getEngineName() {
@@ -35,11 +33,10 @@ public int getEngineRank() {
     /** {@inheritDoc} */
     @Override
     public Engine getEngine() {
-        if (engine == null) {
-            synchronized (OrtEngineProvider.class) {
-                engine = OrtEngine.newInstance();
-            }
-        }
-        return engine;
+        return InstanceHolder.INSTANCE;
+    }
+
+    private static class InstanceHolder {
+        static final Engine INSTANCE = OrtEngine.newInstance();
     }
 }
diff --git a/...paddle/paddlepaddle-engine/src/main/java/ai/djl/paddlepaddle/engine/PpEngineProvider.java b/...paddle/paddlepaddle-engine/src/main/java/ai/djl/paddlepaddle/engine/PpEngineProvider.java
@@ -18,8 +18,6 @@
 /** {@code PpEngineProvider} is the PaddlePaddle implementation of {@link EngineProvider}. */
 public class PpEngineProvider implements EngineProvider {
 
-    private static volatile Engine engine; // NOPMD
-
     /** {@inheritDoc} */
     @Override
     public String getEngineName() {
@@ -35,11 +33,10 @@ public int getEngineRank() {
     /** {@inheritDoc} */
     @Override
     public Engine getEngine() {
-        if (engine == null) {
-            synchronized (PpEngineProvider.class) {
-                engine = PpEngine.newInstance();
-            }
-        }
-        return engine;
+        return InstanceHolder.INSTANCE;
+    }
+
+    private static class InstanceHolder {
+        static final Engine INSTANCE = PpEngine.newInstance();
     }
 }
diff --git a/engines/pytorch/pytorch-engine/src/main/java/ai/djl/pytorch/engine/PtEngineProvider.java b/engines/pytorch/pytorch-engine/src/main/java/ai/djl/pytorch/engine/PtEngineProvider.java
@@ -18,8 +18,6 @@
 /** {@code PtEngineProvider} is the PyTorch implementation of {@link EngineProvider}. */
 public class PtEngineProvider implements EngineProvider {
 
-    private static volatile Engine engine; // NOPMD
-
     /** {@inheritDoc} */
     @Override
     public String getEngineName() {
@@ -35,11 +33,10 @@ public int getEngineRank() {
     /** {@inheritDoc} */
     @Override
     public Engine getEngine() {
-        if (engine == null) {
-            synchronized (PtEngineProvider.class) {
-                engine = PtEngine.newInstance();
-            }
-        }
-        return engine;
+        return InstanceHolder.INSTANCE;
+    }
+
+    private static class InstanceHolder {
+        static final Engine INSTANCE = PtEngine.newInstance();
     }
 }
diff --git a/...tensorflow/tensorflow-engine/src/main/java/ai/djl/tensorflow/engine/TfEngineProvider.java b/...tensorflow/tensorflow-engine/src/main/java/ai/djl/tensorflow/engine/TfEngineProvider.java
@@ -18,8 +18,6 @@
 /** {@code TfEngineProvider} is the TensorFlow implementation of {@link EngineProvider}. */
 public class TfEngineProvider implements EngineProvider {
 
-    private static volatile Engine engine; // NOPMD
-
     /** {@inheritDoc} */
     @Override
     public String getEngineName() {
@@ -35,11 +33,10 @@ public int getEngineRank() {
     /** {@inheritDoc} */
     @Override
     public Engine getEngine() {
-        if (engine == null) {
-            synchronized (TfEngineProvider.class) {
-                engine = TfEngine.newInstance();
-            }
-        }
-        return engine;
+        return InstanceHolder.INSTANCE;
+    }
+
+    private static class InstanceHolder {
+        static final Engine INSTANCE = TfEngine.newInstance();
     }
 }
diff --git a/engines/tensorrt/src/main/java/ai/djl/tensorrt/engine/TrtEngineProvider.java b/engines/tensorrt/src/main/java/ai/djl/tensorrt/engine/TrtEngineProvider.java
@@ -18,8 +18,6 @@
 /** {@code TrtEngineProvider} is the TensorRT implementation of {@link EngineProvider}. */
 public class TrtEngineProvider implements EngineProvider {
 
-    private static volatile Engine engine; // NOPMD
-
     /** {@inheritDoc} */
     @Override
     public String getEngineName() {
@@ -35,11 +33,10 @@ public int getEngineRank() {
     /** {@inheritDoc} */
     @Override
     public Engine getEngine() {
-        if (engine == null) {
-            synchronized (TrtEngineProvider.class) {
-                engine = TrtEngine.newInstance();
-            }
-        }
-        return engine;
+        return InstanceHolder.INSTANCE;
+    }
+
+    private static class InstanceHolder {
+        static final Engine INSTANCE = TrtEngine.newInstance();
     }
 }
diff --git a/engines/tflite/tflite-engine/src/main/java/ai/djl/tflite/engine/TfLiteEngineProvider.java b/engines/tflite/tflite-engine/src/main/java/ai/djl/tflite/engine/TfLiteEngineProvider.java
@@ -18,8 +18,6 @@
 /** {@code TfLiteEngineProvider} is the TFLite implementation of {@link EngineProvider}. */
 public class TfLiteEngineProvider implements EngineProvider {
 
-    private static volatile Engine engine; // NOPMD
-
     /** {@inheritDoc} */
     @Override
     public String getEngineName() {
@@ -35,11 +33,10 @@ public int getEngineRank() {
     /** {@inheritDoc} */
     @Override
     public Engine getEngine() {
-        if (engine == null) {
-            synchronized (TfLiteEngineProvider.class) {
-                engine = TfLiteEngine.newInstance();
-            }
-        }
-        return engine;
+        return InstanceHolder.INSTANCE;
+    }
+
+    private static class InstanceHolder {
+        static final Engine INSTANCE = TfLiteEngine.newInstance();
     }
 }