resolve comments

cpp/src/jni/orc/concurrent_map.h

@@ -33,9 +33,9 @@ namespace jni {
  * @tparam Holder class of the object to hold.
  */
 template <typename Holder>
-class concurrentMap {
+class ConcurrentMap {
  public:
-  concurrentMap() : module_id_(kInitModuleId) {}
+  ConcurrentMap() : module_id_(init_module_id_) {}
 
   jlong Insert(Holder holder) {
     std::lock_guard<std::mutex> lock(mtx_);
@@ -50,20 +50,16 @@ class concurrentMap {
   }
 
   Holder Lookup(jlong module_id) {
-    Holder result = NULLPTR;
-    try {
-      result = map_.at(module_id);
-    } catch (const std::out_of_range& e) {
-    }
-    if (result != NULLPTR) {
-      return result;
+    auto it = map_.find(module_id);
+    if (it != map_.end()) {
+      return it->second;
     }
     std::lock_guard<std::mutex> lock(mtx_);
-    try {
-      result = map_.at(module_id);
-    } catch (const std::out_of_range& e) {
+    it = map_.find(module_id);
+    if (it != map_.end()) {
+      return it->second;
     }
-    return result;
+    return NULLPTR;
   }
 
   void Clear() {
@@ -73,7 +69,7 @@ class concurrentMap {
 
  private:
   // starting value of the module_id.
-  static constexpr int kInitModuleId = 4;
+  static constexpr int init_module_id_ = 4;
 
   int64_t module_id_;
   std::mutex mtx_;

cpp/src/jni/orc/jni_wrapper.cpp

@@ -48,11 +48,11 @@ static jmethodID record_batch_constructor;
 
 static jint JNI_VERSION = JNI_VERSION_1_6;
 
-using arrow::jni::concurrentMap;
+using arrow::jni::ConcurrentMap;
 
-static concurrentMap<std::shared_ptr<arrow::Buffer>> buffer_holder_;
-static concurrentMap<std::shared_ptr<RecordBatchReader>> orc_stripe_reader_holder_;
-static concurrentMap<std::shared_ptr<ORCFileReader>> orc_reader_holder_;
+static ConcurrentMap<std::shared_ptr<arrow::Buffer>> buffer_holder_;
+static ConcurrentMap<std::shared_ptr<RecordBatchReader>> orc_stripe_reader_holder_;
+static ConcurrentMap<std::shared_ptr<ORCFileReader>> orc_reader_holder_;
 
 jclass CreateGlobalClassReference(JNIEnv* env, const char* class_name) {
   jclass local_class = env->FindClass(class_name);

java/adapter/orc/src/main/java/org/apache/arrow/adapter/orc/OrcJniUtils.java

@@ -23,7 +23,6 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.nio.file.Files;
 import java.nio.file.StandardCopyOption;
-import java.util.UUID;
 
 /**
  * Helper class for JNI related operations.
@@ -34,10 +33,6 @@ class OrcJniUtils {
 
   private OrcJniUtils() {}
 
-  /**
-   * Load arrow orc jni library from jar.
-   * @throws IOException throws IOException in case target library can not be found.
-   */
   static void loadOrcAdapterLibraryFromJar()
           throws IOException {
     synchronized (OrcJniUtils.class) {
@@ -53,7 +48,7 @@ class OrcJniUtils {
 
   private static File moveFileFromJarToTemp(final String tmpDir, String libraryToLoad)
           throws IOException {
-    final File temp = setupFile(tmpDir, libraryToLoad);
+    final File temp = File.createTempFile(tmpDir, libraryToLoad);
     try (final InputStream is = OrcReaderJniWrapper.class.getClassLoader()
             .getResourceAsStream(libraryToLoad)) {
       if (is == null) {
@@ -64,10 +59,4 @@ class OrcJniUtils {
     }
     return temp;
   }
-
-  private static File setupFile(String tmpDir, String libraryToLoad)
-          throws IOException {
-    final String randomizeFileName = libraryToLoad + UUID.randomUUID();
-    return File.createTempFile(tmpDir, randomizeFileName);
-  }
 }

java/adapter/orc/src/main/java/org/apache/arrow/adapter/orc/OrcMemoryJniWrapper.java

@@ -46,7 +46,7 @@ class OrcMemoryJniWrapper implements AutoCloseable {
 
   /**
    * Return the size of underlying chunk of memory that has valid data.
-   * @return
+   * @return valid data size
    */
   long getSize() {
     return size;
@@ -54,7 +54,7 @@ class OrcMemoryJniWrapper implements AutoCloseable {
 
   /**
    * Return the size of underlying chunk of memory managed by this OrcMemoryJniWrapper.
-   * @return
+   * @return underlying memory size
    */
   long getCapacity() {
     return capacity;
@@ -62,7 +62,7 @@ class OrcMemoryJniWrapper implements AutoCloseable {
 
   /**
    * Return the memory address of underlying chunk of memory.
-   * @return
+   * @return memory address
    */
   long getMemoryAddress() {
     return memoryAddress;

java/adapter/orc/src/main/java/org/apache/arrow/adapter/orc/OrcReader.java

@@ -32,6 +32,9 @@ public class OrcReader implements AutoCloseable {
   private final OrcReaderJniWrapper jniWrapper;
   private BufferAllocator allocator;
 
+  /**
+   * reference to native reader instance.
+   */
   private final long id;
 
   /**

java/adapter/orc/src/main/java/org/apache/arrow/adapter/orc/OrcStripeReader.java

@@ -40,6 +40,9 @@ import io.netty.buffer.ArrowBuf;
  * Orc stripe that load data into ArrowRecordBatch.
  */
 public class OrcStripeReader extends ArrowReader {
+  /**
+   * reference to native stripe reader instance.
+   */
   private final long id;
   private MessageChannelReader schemaReader;