[RocksJava] Addressed comments in D28971

java/Makefile

@@ -51,7 +51,7 @@ endif
 JAVA_TESTS = org.rocksdb.test.BackupableDBOptionsTest\
         org.rocksdb.test.BackupableDBTest\
 		org.rocksdb.test.BlockBasedTableConfigTest\
-		org.rocksdb.test.CheckpointTest\
+		org.rocksdb.test.CheckPointTest\
 		org.rocksdb.test.ColumnFamilyOptionsTest\
 		org.rocksdb.test.ColumnFamilyTest\
 		org.rocksdb.test.ComparatorOptionsTest\

java/org/rocksdb/Checkpoint.java

@@ -17,15 +17,21 @@ public class Checkpoint extends RocksObject {
    *
    * @param db {@link RocksDB} instance.
    * @return a Checkpoint instance.
+   *
+   * @throws java.lang.IllegalArgumentException if {@link RocksDB}
+   *     instance is null.
+   * @throws java.lang.IllegalStateException if {@link RocksDB}
+   *     instance is not initialized.
    */
   public static Checkpoint create(RocksDB db) {
-    if (db == null || !db.isInitialized()) {
+    if (db == null) {
       throw new IllegalArgumentException(
-          "RocksDB instance needs to be initialized.");
+          "RocksDB instance shall not be null.");
+    } else if (!db.isInitialized()) {
+      throw new IllegalStateException(
+          "RocksDB instance must be initialized.");
     }
-    Checkpoint checkpoint = new Checkpoint(
-        newCheckpoint(db.nativeHandle_));
-    checkpoint.db_ = db;
+    Checkpoint checkpoint = new Checkpoint(db);
     return checkpoint;
   }
 
@@ -50,9 +56,10 @@ public class Checkpoint extends RocksObject {
     disposeInternal(nativeHandle_);
   }
 
-  private Checkpoint(long handle) {
+  private Checkpoint(RocksDB db) {
     super();
-    nativeHandle_ = handle;
+    nativeHandle_ = newCheckpoint(db.nativeHandle_);
+    db_ = db;
   }
 
   RocksDB db_;

java/org/rocksdb/test/CheckPointTest.java

@@ -12,7 +12,7 @@ import org.rocksdb.RocksDBException;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-public class CheckpointTest {
+public class CheckPointTest {
 
   @ClassRule
   public static final RocksMemoryResource rocksMemoryResource =
@@ -74,7 +74,7 @@ public class CheckpointTest {
     Checkpoint.create(null);
   }
 
-  @Test(expected = IllegalArgumentException.class)
+  @Test(expected = IllegalStateException.class)
   public void failIfDbNotInitialized() throws RocksDBException {
     RocksDB db = RocksDB.open(dbFolder.getRoot().getAbsolutePath());
     db.dispose();

java/rocksjni/checkpoint.cc

@@ -58,4 +58,4 @@ void Java_org_rocksdb_Checkpoint_createCheckpoint(
   if (!s.ok()) {
       rocksdb::RocksDBExceptionJni::ThrowNew(env, s);
   }
-}
+}