DRILL-6389: Fixed building javadocs

 - Added documentation about how to build javadocs
 - Fixed some of the javadoc warnings

closes #1276

30 files changed, 72 insertions, 84 deletions

diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/client/DrillClient.java b/exec/java-exec/src/main/java/org/apache/drill/exec/client/DrillClient.java
index f880b936c..ccd7e3636 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/client/DrillClient.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/client/DrillClient.java
@@ -520,7 +520,7 @@ public class DrillClient implements Closeable, ConnectionThrottle {
    *
    * @return the server name, or null if not connected or if the server
    *         doesn't provide the name
-   * @return
+   * @return The server name.
    */
   public String getServerName() {
     return (client != null && client.getServerInfos() != null) ? client.getServerInfos().getName() : null;
@@ -533,7 +533,7 @@ public class DrillClient implements Closeable, ConnectionThrottle {
    *
    * @return the server version, or null if not connected or if the server
    *         doesn't provide the version
-   * @return
+   * @return The server version.
    */
   public Version getServerVersion() {
     return (client != null && client.getServerInfos() != null) ? UserRpcUtils.getVersion(client.getServerInfos()) : null;
@@ -588,7 +588,7 @@ public class DrillClient implements Closeable, ConnectionThrottle {
    * @param type
    * @param query
    * @param isSplitPlan - option to tell whether to return single or split plans for a query
-   * @return list of PlanFragments that can be used later on in {@link #runQuery(QueryType, List, UserResultsListener)}
+   * @return list of PlanFragments that can be used later on in {@link #runQuery(org.apache.drill.exec.proto.UserBitShared.QueryType, java.util.List, org.apache.drill.exec.rpc.user.UserResultsListener)}
    * to run a query without additional planning
    */
   public DrillRpcFuture<QueryPlanFragments> planQuery(QueryType type, String query, boolean isSplitPlan) {
@@ -663,7 +663,7 @@ public class DrillClient implements Closeable, ConnectionThrottle {
    * Get the list of catalogs in <code>INFORMATION_SCHEMA.CATALOGS</code> table satisfying the given filters.
    *
    * @param catalogNameFilter Filter on <code>catalog name</code>. Pass null to apply no filter.
-   * @return
+   * @return The list of catalogs in <code>INFORMATION_SCHEMA.CATALOGS</code> table satisfying the given filters.
    */
   public DrillRpcFuture<GetCatalogsResp> getCatalogs(LikeFilter catalogNameFilter) {
     final GetCatalogsReq.Builder reqBuilder = GetCatalogsReq.newBuilder();
@@ -679,7 +679,7 @@ public class DrillClient implements Closeable, ConnectionThrottle {
    *
    * @param catalogNameFilter Filter on <code>catalog name</code>. Pass null to apply no filter.
    * @param schemaNameFilter Filter on <code>schema name</code>. Pass null to apply no filter.
-   * @return
+   * @return The list of schemas in <code>INFORMATION_SCHEMA.SCHEMATA</code> table satisfying the given filters.
    */
   public DrillRpcFuture<GetSchemasResp> getSchemas(LikeFilter catalogNameFilter, LikeFilter schemaNameFilter) {
     final GetSchemasReq.Builder reqBuilder = GetSchemasReq.newBuilder();
@@ -701,7 +701,7 @@ public class DrillClient implements Closeable, ConnectionThrottle {
    * @param schemaNameFilter Filter on <code>schema name</code>. Pass null to apply no filter.
    * @param tableNameFilter Filter in <code>table name</code>. Pass null to apply no filter.
    * @param tableTypeFilter Filter in <code>table type</code>. Pass null to apply no filter
-   * @return
+   * @return The list of tables in <code>INFORMATION_SCHEMA.TABLES</code> table satisfying the given filters.
    */
   public DrillRpcFuture<GetTablesResp> getTables(LikeFilter catalogNameFilter, LikeFilter schemaNameFilter,
       LikeFilter tableNameFilter, List<String> tableTypeFilter) {
@@ -732,7 +732,7 @@ public class DrillClient implements Closeable, ConnectionThrottle {
    * @param schemaNameFilter Filter on <code>schema name</code>. Pass null to apply no filter.
    * @param tableNameFilter Filter in <code>table name</code>. Pass null to apply no filter.
    * @param columnNameFilter Filter in <code>column name</code>. Pass null to apply no filter.
-   * @return
+   * @return The list of columns in <code>INFORMATION_SCHEMA.COLUMNS</code> table satisfying the given filters.
    */
   public DrillRpcFuture<GetColumnsResp> getColumns(LikeFilter catalogNameFilter, LikeFilter schemaNameFilter,
       LikeFilter tableNameFilter, LikeFilter columnNameFilter) {
@@ -757,10 +757,10 @@ public class DrillClient implements Closeable, ConnectionThrottle {
   }
 
   /**
-   * Create a prepared statement for given <code>query</code>.
+   * Create a prepared statement for given the <code>query</code>.
    *
    * @param query
-   * @return
+   * @return The prepared statement for given the <code>query</code>.
    */
   public DrillRpcFuture<CreatePreparedStatementResp> createPreparedStatement(final String query) {
     final CreatePreparedStatementReq req =
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/expr/CodeGenerator.java b/exec/java-exec/src/main/java/org/apache/drill/exec/expr/CodeGenerator.java
index 480b2c2ea..76d68e22d 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/expr/CodeGenerator.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/expr/CodeGenerator.java
@@ -46,7 +46,7 @@ import com.sun.codemodel.JDefinedClass;
  * class without the normal byte-code manipulations. Plain Java allows
  * the option to persist, and debug, the generated code when building new
  * generated classes or otherwise working with generated code. To turn
- * on debugging, see the explanation in {@link ClassBuilder}.
+ * on debugging, see the explanation in {@link org.apache.drill.exec.compile.ClassBuilder}.
  *
  * @param <T>
  *          The interface that results from compiling and merging the runtime
@@ -149,7 +149,7 @@ public class CodeGenerator<T> {
   /**
    * Debug-time option to persist the code for the generated class to permit debugging.
    * Has effect only when code is generated using the plain Java option. Code
-   * is written to the code directory specified in {@link ClassBuilder}.
+   * is written to the code directory specified in {@link org.apache.drill.exec.compile.ClassBuilder}.
    * To debug code, set this option, then point your IDE to the code directory
    * when the IDE prompts you for the source code location.
    *
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/FunctionLookupContext.java b/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/FunctionLookupContext.java
index 944041e80..872c13780 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/FunctionLookupContext.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/FunctionLookupContext.java
@@ -41,7 +41,7 @@ public interface FunctionLookupContext {
    * implementations found on classpath.
    *
    * @param functionCall - Specifies function name and type of arguments
-   * @return
+   * @return AbstractFuncHolder
    */
   public AbstractFuncHolder findNonDrillFunction(FunctionCall functionCall);
 }
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/ModifiedUnparseVisitor.java b/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/ModifiedUnparseVisitor.java
index 58e3c3a1f..fe8349057 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/ModifiedUnparseVisitor.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/ModifiedUnparseVisitor.java
@@ -43,7 +43,7 @@ public class ModifiedUnparseVisitor extends UnparseVisitor {
   }
 
   /**
-   * Unparse the given {@link Java.CompilationUnit} to the given {@link Writer}.
+   * Unparse the given {@link org.codehaus.janino.Java.CompilationUnit} to the given {@link java.io.Writer}.
    */
   public static void unparse(Java.CompilationUnit cu, Writer w) {
     UnparseVisitor.unparse(cu, w);
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/ops/QueryContext.java b/exec/java-exec/src/main/java/org/apache/drill/exec/ops/QueryContext.java
index eb32bc650..07742f2e8 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/ops/QueryContext.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/ops/QueryContext.java
@@ -163,10 +163,10 @@ public class QueryContext implements AutoCloseable, OptimizerRulesContext, Schem
   }
 
   /**
-   *  Create and return a SchemaTree with given <i>schemaConfig</i> but some schemas (from storage plugins)
+   *  Create and return a {@link org.apache.calcite.schema.SchemaPlus} with given <i>schemaConfig</i> but some schemas (from storage plugins)
    *  could be initialized later.
    * @param schemaConfig
-   * @return
+   * @return A {@link org.apache.calcite.schema.SchemaPlus} with given <i>schemaConfig</i>.
    */
   public SchemaPlus getRootSchema(SchemaConfig schemaConfig) {
     return schemaTreeProvider.createRootSchema(schemaConfig);
@@ -174,7 +174,7 @@ public class QueryContext implements AutoCloseable, OptimizerRulesContext, Schem
   /**
    *  Create and return a fully initialized SchemaTree with given <i>schemaConfig</i>.
    * @param schemaConfig
-   * @return
+   * @return A fully initialized SchemaTree with given <i>schemaConfig</i>.
    */
 
   public SchemaPlus getFullRootSchema(SchemaConfig schemaConfig) {
@@ -182,7 +182,7 @@ public class QueryContext implements AutoCloseable, OptimizerRulesContext, Schem
   }
   /**
    * Get the user name of the user who issued the query that is managed by this QueryContext.
-   * @return
+   * @return The user name of the user who issued the query that is managed by this QueryContext.
    */
   @Override
   public String getQueryUserName() {
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractExchange.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractExchange.java
index 788516145..96bdbaa34 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractExchange.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractExchange.java
@@ -55,7 +55,7 @@ public abstract class AbstractExchange extends AbstractSingle implements Exchang
   /**
    * Default sender parallelization width range is [1, Integer.MAX_VALUE] and no endpoint affinity
    * @param receiverFragmentEndpoints Endpoints assigned to receiver fragment if available, otherwise an empty list.
-   * @return
+   * @return Sender {@link org.apache.drill.exec.planner.fragment.ParallelizationInfo}.
    */
   @Override
   public ParallelizationInfo getSenderParallelizationInfo(List<DrillbitEndpoint> receiverFragmentEndpoints) {
@@ -66,7 +66,7 @@ public abstract class AbstractExchange extends AbstractSingle implements Exchang
    * Default receiver parallelization width range is [1, Integer.MAX_VALUE] and affinity to nodes where sender
    * fragments are running.
    * @param senderFragmentEndpoints Endpoints assigned to receiver fragment if available, otherwise an empty list.
-   * @return
+   * @return Receiver {@link org.apache.drill.exec.planner.fragment.ParallelizationInfo}.
    */
   @Override
   public ParallelizationInfo getReceiverParallelizationInfo(List<DrillbitEndpoint> senderFragmentEndpoints) {
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractSingle.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractSingle.java
index 1021465c3..9f3654e8e 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractSingle.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractSingle.java
@@ -26,7 +26,6 @@ import com.google.common.collect.Iterators;
 
 /**
  * Describes an operator that expects a single child operator as its input.
- * @param <T> The type of Exec model supported.
  */
 public abstract class AbstractSingle extends AbstractBase {
   static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(AbstractSingle.class);
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Exchange.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Exchange.java
index 0aa3b70ab..56e9b9c90 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Exchange.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Exchange.java
@@ -83,7 +83,7 @@ public interface Exchange extends PhysicalOperator {
    * max width and affinity to Drillbits.
    *
    * @param receiverFragmentEndpoints Endpoints assigned to receiver fragment if available, otherwise an empty list.
-   * @return
+   * @return Sender {@link org.apache.drill.exec.planner.fragment.ParallelizationInfo}.
    */
   @JsonIgnore
   ParallelizationInfo getSenderParallelizationInfo(List<DrillbitEndpoint> receiverFragmentEndpoints);
@@ -93,7 +93,7 @@ public interface Exchange extends PhysicalOperator {
    * max width and affinity to Drillbits.
    *
    * @param senderFragmentEndpoints Endpoints assigned to receiver fragment if available, otherwise an empty list
-   * @return
+   * @return Receiver {@link org.apache.drill.exec.planner.fragment.ParallelizationInfo}.
    */
   @JsonIgnore
   ParallelizationInfo getReceiverParallelizationInfo(List<DrillbitEndpoint> senderFragmentEndpoints);
@@ -101,7 +101,7 @@ public interface Exchange extends PhysicalOperator {
   /**
    * Return the feeding child of this operator node.
    *
-   * @return
+   * @return The feeding child of this operator node.
    */
   PhysicalOperator getChild();
 
@@ -110,4 +110,4 @@ public interface Exchange extends PhysicalOperator {
    */
   @JsonIgnore
   ParallelizationDependency getParallelizationDependency();
-}
\ No newline at end of file
+}
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/LateralContract.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/LateralContract.java
index 52e601e6f..2f6d20dd7 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/LateralContract.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/LateralContract.java
@@ -27,19 +27,20 @@ import org.apache.drill.exec.record.RecordBatch.IterOutcome;
 public interface LateralContract {
 
   /**
-   * Get reference to left side incoming of LateralJoinRecordBatch
-   * @return
+   * Get reference to left side incoming of {@link org.apache.drill.exec.physical.impl.join.LateralJoinBatch}.
+   * @return The incoming {@link org.apache.drill.exec.record.RecordBatch}
    */
   RecordBatch getIncoming();
 
   /**
-   * Get current record index in incoming to be processed
-   * @return
+   * Get current record index in incoming to be processed.
+   * @return The current record index in incoming to be processed.
    */
   int getRecordIndex();
 
   /**
-   * Get the current outcome of left incoming batch
+   * Get the current outcome of left incoming batch.
+   * @return The current outcome of left incoming batch.
    */
   IterOutcome getLeftOutcome();
 }
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/PhysicalOperator.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/PhysicalOperator.java
index 35138c85e..82fb53bf4 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/PhysicalOperator.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/PhysicalOperator.java
@@ -43,16 +43,13 @@ public interface PhysicalOperator extends GraphValue<PhysicalOperator> {
    * Describes whether or not a particular physical operator can actually be executed. Most physical operators can be
    * executed. However, Exchange nodes cannot be executed. In order to be executed, they must be converted into their
    * Exec sub components.
-   *
-   * @return
    */
   @JsonIgnore
   boolean isExecutable();
 
   /**
    * Describes the SelectionVector Mode for the output steam from this physical op.
-   * This property is used during physical plan creating using {@link PhysicalPlanCreator}.
-   * @return
+   * This property is used during physical plan creating using {@link org.apache.drill.exec.planner.physical.PhysicalPlanCreator}.
    */
   @JsonIgnore
   SelectionVectorMode getSVMode();
@@ -61,14 +58,12 @@ public interface PhysicalOperator extends GraphValue<PhysicalOperator> {
    * Provides capability to build a set of output based on traversing a query graph tree.
    *
    * @param physicalVisitor
-   * @return
    */
   <T, X, E extends Throwable> T accept(PhysicalVisitor<T, X, E> physicalVisitor, X value) throws E;
 
   /**
    * Regenerate with this node with a new set of children.  This is used in the case of materialization or optimization.
    * @param children
-   * @return
    */
   @JsonIgnore
   PhysicalOperator getNewWithChildren(List<PhysicalOperator> children) throws ExecutionSetupException;
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Sender.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Sender.java
index c39cc9b0c..340cbcef6 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Sender.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Sender.java
@@ -38,7 +38,7 @@ public interface Sender extends FragmentRoot {
 
   /**
    * Get the receiver major fragment id that is opposite this sender.
-   * @return
+   * @return The receiver major fragment id that is opposite this sender.
    */
   @JsonProperty("receiver-major-fragment")
   public int getOppositeMajorFragmentId();
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Store.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Store.java
index ffec99e74..24338e0bf 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Store.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/Store.java
@@ -61,14 +61,14 @@ public interface Store extends HasAffinity {
    * maxWidth value of 1 will be returned. In the case that there is no limit for parallelization, this method should
    * return Integer.MAX_VALUE.
    *
-   * @return
+   * @return The maximum allowable width for the Store operation.
    */
   @JsonIgnore
   public abstract int getMaxWidth();
 
   /**
    * Get the child of this store operator as this will be needed for parallelization materialization purposes.
-   * @return
+   * @return The child of this store operator.
    */
   public abstract PhysicalOperator getChild();
-}
\ No newline at end of file
+}
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/xsort/MSortTemplate.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/xsort/MSortTemplate.java
index afbc58bb2..49746264b 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/xsort/MSortTemplate.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/xsort/MSortTemplate.java
@@ -90,7 +90,7 @@ public abstract class MSortTemplate implements MSorter, IndexedSortable {
    * ExternalSortBatch to make decisions about whether to spill or not.
    *
    * @param recordCount
-   * @return
+   * @return The amount of memory MSorter needs for a given record count.
    */
   public static long memoryNeeded(final int recordCount) {
     // We need 4 bytes (SV4) for each record, power of 2 rounded.
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/xsort/managed/MergeSortWrapper.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/xsort/managed/MergeSortWrapper.java
index bca28f177..7ac00ea45 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/xsort/managed/MergeSortWrapper.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/xsort/managed/MergeSortWrapper.java
@@ -97,9 +97,7 @@ public class MergeSortWrapper extends BaseSortWrapper implements SortResults {
    * destination container, indexed by an SV4.
    *
    * @param batchGroups the complete set of in-memory batches
-   * @param batch the record batch (operator) for the sort operator
-   * @param destContainer the vector container for the sort operator
-   * @return the sv4 for this operator
+   * @param outputBatchSize
    */
 
   public void merge(List<BatchGroup.InputBatch> batchGroups, int outputBatchSize) {
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/rowSet/model/TupleModel.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/rowSet/model/TupleModel.java
index 767153ab7..28b1d937b 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/rowSet/model/TupleModel.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/rowSet/model/TupleModel.java
@@ -46,11 +46,11 @@ import org.apache.drill.exec.record.metadata.TupleMetadata;
  * <dt>Visitor</dt>
  * <dd>The visitor abstraction (classic Gang-of-Four pattern) allows adding
  * functionality without complicating the structure classes. Allows the same
- * abstraction to be used for the testing {@link RowSet} abstractions and
+ * abstraction to be used for the testing <b>RowSet</b> abstractions and
  * the scan operator "loader" classes.</dd>
  * <dt>Metadata</dt>
  * <dd>Metadata is simply data about data. Here, data about tuples and columns.
- * The column metadata mostly expands on that available in {@link MaterializedField},
+ * The column metadata mostly expands on that available in {@link org.apache.drill.exec.record.MaterializedField},
  * but also adds allocation hints.
  * </dl>
  * <p>
@@ -60,7 +60,7 @@ import org.apache.drill.exec.record.metadata.TupleMetadata;
  * metadata and visitor behavior to allow much easier processing that is
  * possible with the raw container structure.
  * <p>
- * A key value of this abstraction is the extended {@link TupleSchema}
+ * A key value of this abstraction is the extended {@link org.apache.drill.exec.record.metadata.TupleSchema}
  * associated with the structure.  Unlike a
  * {@link VectorContainer}, this abstraction keeps the schema in sync
  * with vectors as columns are added.
@@ -72,7 +72,7 @@ import org.apache.drill.exec.record.metadata.TupleMetadata;
  * <p>
  * Tuples provide access to columns by both index and name. Both the schema and
  * model classes follow this convention. Compared with the VectorContainer and
- * {@link AbstractMapVector} classes, the vector index is a first-class concept:
+ * {@link org.apache.drill.exec.vector.complex.AbstractMapVector} classes, the vector index is a first-class concept:
  * the column model and schema are guaranteed to reside at the same index relative
  * to the enclosing tuple. In addition, name access is efficient using a hash
  * index.
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/rowSet/model/single/VectorAllocator.java b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/rowSet/model/single/VectorAllocator.java
index f4fc5d495..b9c064a31 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/physical/rowSet/model/single/VectorAllocator.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/physical/rowSet/model/single/VectorAllocator.java
@@ -36,9 +36,10 @@ import org.apache.drill.exec.vector.complex.RepeatedMapVector;
  * walk the schema tree to allocate new vectors according to a given
  * row count and the size information provided in column metadata.
  * <p>
- * @see {@link AllocationHelper} - the class which this one replaces
- * @see {@link org.apache.drill.exec.record.VectorInitializer} - an earlier cut at implementation
- * based on data from the {@link org.apache.drill.exec.record.RecordBatchSizer}
+ *   {@link org.apache.drill.exec.vector.AllocationHelper} - the class which this one replaces
+ *   {@link org.apache.drill.exec.record.VectorInitializer} - an earlier cut at implementation
+ *   based on data from the {@link org.apache.drill.exec.record.RecordBatchSizer}
+ * </p>
  */
 
 // TODO: Does not yet handle lists; lists are a simple extension
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/AbstractPartitionDescriptor.java b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/AbstractPartitionDescriptor.java
index 412841a21..b70c764e2 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/AbstractPartitionDescriptor.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/AbstractPartitionDescriptor.java
@@ -31,7 +31,7 @@ public abstract class AbstractPartitionDescriptor implements PartitionDescriptor
 
   /**
    * A sequence of sublists of partition locations combined into a single super list.
-   * The size of each sublist is at most {@link PartitionDescriptor.PARTITION_BATCH_SIZE}
+   * The size of each sublist is at most {@link PartitionDescriptor#PARTITION_BATCH_SIZE}
    * For example if the size is 3, the complete list could be: {(a, b, c), {d, e, f), (g, h)}
    */
   protected List<List<PartitionLocation>> locationSuperList;
@@ -42,7 +42,7 @@ public abstract class AbstractPartitionDescriptor implements PartitionDescriptor
 
   /**
    * Create sublists of the partition locations, each sublist of size
-   * at most {@link PartitionDescriptor.PARTITION_BATCH_SIZE}
+   * at most {@link PartitionDescriptor#PARTITION_BATCH_SIZE}
    */
   protected abstract void createPartitionSublists() ;
 
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/DFSFilePartitionLocation.java b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/DFSFilePartitionLocation.java
index 228ae6be8..ecfa6220d 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/DFSFilePartitionLocation.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/DFSFilePartitionLocation.java
@@ -51,7 +51,7 @@ public class DFSFilePartitionLocation extends SimplePartitionLocation {
   /**
    * Returns the value for a give partition key
    * @param index - Index of the partition key whose value is to be returned
-   * @return
+   * @return The value for a partition.
    */
   @Override
   public String getPartitionValue(int index) {
@@ -61,7 +61,7 @@ public class DFSFilePartitionLocation extends SimplePartitionLocation {
 
   /**
    * Return the full location of this partition
-   * @return
+   * @return The partition location.
    */
   @Override
   public String getEntirePartitionLocation() {
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/PartitionDescriptor.java b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/PartitionDescriptor.java
index b29f02e01..220bf291e 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/PartitionDescriptor.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/PartitionDescriptor.java
@@ -70,7 +70,6 @@ public interface PartitionDescriptor extends Iterable<List<PartitionLocation>> {
    * Method returns the Major type associated with the given column
    * @param column - column whose type should be determined
    * @param plannerSettings
-   * @return
    */
   TypeProtos.MajorType getVectorType(SchemaPath column, PlannerSettings plannerSettings);
 
@@ -78,7 +77,6 @@ public interface PartitionDescriptor extends Iterable<List<PartitionLocation>> {
    * Methods create a new TableScan rel node, given the lists of new partitions or new files to SCAN.
    * @param newPartitions
    * @param wasAllPartitionsPruned
-   * @return
    * @throws Exception
    */
   public TableScan createTableScan(List<PartitionLocation> newPartitions,
@@ -91,7 +89,6 @@ public interface PartitionDescriptor extends Iterable<List<PartitionLocation>> {
    * @param cacheFileRoot
    * @param wasAllPartitionsPruned
    * @param metaContext
-   * @return
    * @throws Exception
    */
   public TableScan createTableScan(List<PartitionLocation> newPartitions, String cacheFileRoot,
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/DistributionAffinity.java b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/DistributionAffinity.java
index 5ebea255f..b1ab9aab6 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/DistributionAffinity.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/DistributionAffinity.java
@@ -55,7 +55,7 @@ public enum DistributionAffinity {
   /**
    * Is the current DistributionAffinity less restrictive than the given DistributionAffinity?
    * @param distributionAffinity
-   * @return
+   * @return True if the current DistributionAffinity less restrictive than the given DistributionAffinity. False otherwise.
    */
   public boolean isLessRestrictiveThan(final DistributionAffinity distributionAffinity) {
     return ordinal() < distributionAffinity.ordinal();
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/SimpleParallelizer.java b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/SimpleParallelizer.java
index 1ee9ea231..274db31eb 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/SimpleParallelizer.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/SimpleParallelizer.java
@@ -140,7 +140,7 @@ public class SimpleParallelizer implements ParallelizationParameters {
    * @param rootFragment
    * @param session
    * @param queryContextInfo
-   * @return
+   * @return The {@link QueryWorkUnit}s.
    * @throws ExecutionSetupException
    */
   public List<QueryWorkUnit> getSplitFragments(OptionList options, DrillbitEndpoint foremanNode, QueryId queryId,
@@ -154,7 +154,7 @@ public class SimpleParallelizer implements ParallelizationParameters {
    * Helper method to reuse the code for QueryWorkUnit(s) generation
    * @param activeEndpoints
    * @param rootFragment
-   * @return
+   * @return A {@link PlanningSet}.
    * @throws ExecutionSetupException
    */
   protected PlanningSet getFragmentsHelper(Collection<DrillbitEndpoint> activeEndpoints, Fragment rootFragment) throws ExecutionSetupException {
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/Wrapper.java b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/Wrapper.java
index 3ff00ca6e..329a8a189 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/Wrapper.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/fragment/Wrapper.java
@@ -184,15 +184,15 @@ public class Wrapper {
 
   /**
    * Is the endpoints assignment done for this fragment?
-   * @return
+   * @return True if the endpoints assignment done for this fragment. False otherwise.
    */
   public boolean isEndpointsAssignmentDone() {
     return endpointsAssigned;
   }
 
   /**
-   * Get the list of fragements this particular fragment depends for determining its
-   * @return
+   * Get the list of fragements this particular fragment depends on.
+   * @return The list of fragements this particular fragment depends on.
    */
   public List<Wrapper> getFragmentDependencies() {
     return ImmutableList.copyOf(fragmentDependencies);
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/handlers/SqlHandlerUtil.java b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/handlers/SqlHandlerUtil.java
index 02f611481..b7c7ff380 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/handlers/SqlHandlerUtil.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/handlers/SqlHandlerUtil.java
@@ -237,7 +237,7 @@ public class SqlHandlerUtil {
   /**
    * Drops table from schema.
    * If drop has failed makes concurrency check: checks if table still exists.
-   * If table exists, throws {@link @UserException} since drop was unsuccessful,
+   * If table exists, throws {@link org.apache.drill.common.exceptions.UserException} since drop was unsuccessful,
    * otherwise assumes that other user had dropped the view and exists without error.
    *
    * @param drillSchema drill schema
@@ -256,7 +256,7 @@ public class SqlHandlerUtil {
   /**
    * Drops view from schema.
    * If drop has failed makes concurrency check: checks if view still exists.
-   * If view exists, throws {@link @UserException} since drop was unsuccessful,
+   * If view exists, throws {@link org.apache.drill.common.exceptions.UserException} since drop was unsuccessful,
    * otherwise assumes that other user had dropped the view and exists without error.
    *
    * @param drillSchema drill schema
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/store/StoragePlugin.java b/exec/java-exec/src/main/java/org/apache/drill/exec/store/StoragePlugin.java
index 2969d4f43..50f273102 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/store/StoragePlugin.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/store/StoragePlugin.java
@@ -54,7 +54,7 @@ public interface StoragePlugin extends SchemaFactory, AutoCloseable {
    *
    * @param userName User whom to impersonate when when reading the contents as part of Scan.
    * @param selection The configured storage engine specific selection.
-   * @return
+   * @return The physical scan operator for the particular GroupScan (read) node.
    * @throws IOException
    */
   public AbstractGroupScan getPhysicalScan(String userName, JSONOptions selection) throws IOException;
@@ -65,7 +65,7 @@ public interface StoragePlugin extends SchemaFactory, AutoCloseable {
    * @param userName User whom to impersonate when when reading the contents as part of Scan.
    * @param selection The configured storage engine specific selection.
    * @param columns (optional) The list of column names to scan from the data source.
-   * @return
+   * @return The physical scan operator for the particular GroupScan (read) node.
    * @throws IOException
   */
   public AbstractGroupScan getPhysicalScan(String userName, JSONOptions selection, List<SchemaPath> columns)
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/store/easy/text/compliant/TextParsingSettings.java b/exec/java-exec/src/main/java/org/apache/drill/exec/store/easy/text/compliant/TextParsingSettings.java
index a01a08214..4bc24bdd2 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/store/easy/text/compliant/TextParsingSettings.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/store/easy/text/compliant/TextParsingSettings.java
@@ -209,7 +209,7 @@ public class TextParsingSettings {
 
   /**
    * Configures how to handle unescaped quotes inside quoted values. If set to {@code true}, the parser will parse the quote normally as part of the value.
-   * If set the {@code false}, a {@link TextParsingException} will be thrown. Defaults to {@code true}.
+   * If set the {@code false}, a {@link com.univocity.parsers.common.TextParsingException} will be thrown. Defaults to {@code true}.
    * @param parseUnescapedQuotes indicates whether or not the CSV parser should accept unescaped quotes inside quoted values.
    */
   public void setParseUnescapedQuotes(boolean parseUnescapedQuotes) {
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/metadata/MetadataVersion.java b/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/metadata/MetadataVersion.java
index 15b4b9da3..797208638 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/metadata/MetadataVersion.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/metadata/MetadataVersion.java
@@ -106,7 +106,7 @@ public class MetadataVersion implements Comparable<MetadataVersion> {
 /**
  * Supported metadata versions.
  * <p>
- * Note: keep them synchronized with {@link Metadata.ParquetTableMetadataBase} versions
+ * Note: keep them synchronized with {@link org.apache.drill.exec.store.parquet.metadata.MetadataBase.ParquetTableMetadataBase} versions
  */
   public static class Constants {
     /**
@@ -134,7 +134,7 @@ public class MetadataVersion implements Comparable<MetadataVersion> {
 
     /**
      * Version 3.2: An array with the components of the field name in
-     * {@link Metadata.ColumnTypeMetadata_v3.Key} class is replaced by the SchemaPath.<br>
+     * {@link org.apache.drill.exec.store.parquet.metadata.Metadata_V3.ColumnTypeMetadata_v3.Key} class is replaced by the {@link org.apache.drill.common.expression.SchemaPath}.<br>
      * See DRILL-4264
      */
     public static final String V3_2 = "3.2";
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/util/ImpersonationUtil.java b/exec/java-exec/src/main/java/org/apache/drill/exec/util/ImpersonationUtil.java
index b74ce1aee..c9039e9b0 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/util/ImpersonationUtil.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/util/ImpersonationUtil.java
@@ -110,7 +110,6 @@ public class ImpersonationUtil {
    * @param opUserName Name of the user whom to impersonate while setting up the operator.
    * @param queryUserName Name of the user who issues the query. If <i>opUserName</i> is invalid,
    *                      then this parameter must be valid user name.
-   * @return
    */
   public static UserGroupInformation createProxyUgi(String opUserName, String queryUserName) {
     if (!Strings.isNullOrEmpty(opUserName)) {
@@ -131,7 +130,6 @@ public class ImpersonationUtil {
    * Create and return proxy user {@link org.apache.hadoop.security.UserGroupInformation} for give user name.
    *
    * @param proxyUserName Proxy user name (must be valid)
-   * @return
    */
   public static UserGroupInformation createProxyUgi(String proxyUserName) {
     try {
@@ -202,7 +200,6 @@ public class ImpersonationUtil {
    *
    * @param proxyUserName Name of the user whom to impersonate while accessing the FileSystem contents.
    * @param fsConf FileSystem configuration.
-   * @return
    */
   public static DrillFileSystem createFileSystem(String proxyUserName, Configuration fsConf) {
     return createFileSystem(createProxyUgi(proxyUserName), fsConf, null);
@@ -234,7 +231,7 @@ public class ImpersonationUtil {
    * @param userName User who is checked for administrative privileges.
    * @param adminUsers Comma separated list of admin usernames,
    * @param adminGroups Comma separated list of admin usergroups
-   * @return
+   * @return True if the user has admin priveleges. False otherwise.
    */
   public static boolean hasAdminPrivileges(final String userName, final String adminUsers, final String adminGroups) {
     // Process user is by default an admin
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/util/Utilities.java b/exec/java-exec/src/main/java/org/apache/drill/exec/util/Utilities.java
index a165d9e32..f8fb8d77a 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/util/Utilities.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/util/Utilities.java
@@ -56,11 +56,11 @@ public class Utilities {
   }
 
   /**
-   * Create QueryContextInformation with given <i>defaultSchemaName</i>. Rest of the members of the
+   * Create {@link org.apache.drill.exec.proto.BitControl.QueryContextInformation} with given <i>defaultSchemaName</i>. Rest of the members of the
    * QueryContextInformation is derived from the current state of the process.
    *
    * @param defaultSchemaName
-   * @return
+   * @return A {@link org.apache.drill.exec.proto.BitControl.QueryContextInformation} with given <i>defaultSchemaName</i>.
    */
   public static QueryContextInformation createQueryContextInfo(final String defaultSchemaName, final String sessionId) {
     final long queryStartTime = System.currentTimeMillis();
@@ -75,7 +75,7 @@ public class Utilities {
 
   /**
    * Read the manifest file and get the Drill version number
-   * @return
+   * @return The Drill version.
    */
   public static String getDrillVersion() {
       String v = Utilities.class.getPackage().getImplementationVersion();
@@ -85,7 +85,7 @@ public class Utilities {
   /**
    * Return true if list of schema path has star column.
    * @param projected
-   * @return
+   * @return True if the list of {@link org.apache.drill.common.expression.SchemaPath}s has star column.
    */
   public static boolean isStarQuery(Collection<SchemaPath> projected) {
     return Iterables.tryFind(Preconditions.checkNotNull(projected, COL_NULL_ERROR), new Predicate<SchemaPath>() {
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/vector/accessor/SqlAccessor.java b/exec/java-exec/src/main/java/org/apache/drill/exec/vector/accessor/SqlAccessor.java
index 70fb90eb4..50a257281 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/vector/accessor/SqlAccessor.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/vector/accessor/SqlAccessor.java
@@ -43,12 +43,12 @@ import org.apache.drill.common.types.TypeProtos.MajorType;
  * </p>
  * <li>
  *   a get method that return primitive type throws an exception (callers are
- *   responsible for calling {@link isNull} to check for null before calling
+ *   responsible for calling {@link #isNull(int)} to check for null before calling
  *   such methods)
  * </li>
  * <li>
  *   a get method that returns a non-primitive type returns Java {@code null}
- *   (the caller does not need to call {@link isNull} to check for nulls)
+ *   (the caller does not need to call {@link #isNull(int)} to check for nulls)
  * </li>
  */
 public interface SqlAccessor {
@@ -129,4 +129,4 @@ public interface SqlAccessor {
   /** (See {@link SqlAccessor class description}.) */
   Object getObject(int rowOffset) throws InvalidAccessException;
 
-}
\ No newline at end of file
+}
diff --git a/exec/java-exec/src/test/java/org/apache/drill/exec/physical/unit/PhysicalOpUnitTestBase.java b/exec/java-exec/src/test/java/org/apache/drill/exec/physical/unit/PhysicalOpUnitTestBase.java
index b8a219ba6..d0875ba1c 100644
--- a/exec/java-exec/src/test/java/org/apache/drill/exec/physical/unit/PhysicalOpUnitTestBase.java
+++ b/exec/java-exec/src/test/java/org/apache/drill/exec/physical/unit/PhysicalOpUnitTestBase.java
@@ -487,12 +487,12 @@ public class PhysicalOpUnitTestBase extends ExecTest {
   }
 
   /**
-   * Create JSONRecordReader from input strings.
+   * Create {@link org.apache.drill.exec.store.easy.json.JSONRecordReader} from input strings.
    * @param jsonBatches : list of input strings, each element represent a batch. Each string could either
    *                    be in the form of "[{...}, {...}, ..., {...}]", or in the form of "{...}".
    * @param fragContext : fragment context
    * @param columnsToRead : list of schema paths to read from JSON reader.
-   * @return
+   * @return The {@link org.apache.drill.exec.store.easy.json.JSONRecordReader} corresponding to each given jsonBatch.
    */
   public static Iterator<RecordReader> getJsonReadersFromBatchString(List<String> jsonBatches, FragmentContext fragContext, List<SchemaPath> columnsToRead) {
     ObjectMapper mapper = new ObjectMapper();
@@ -515,7 +515,7 @@ public class PhysicalOpUnitTestBase extends ExecTest {
    * @param inputPaths : list of .json file paths.
    * @param fragContext
    * @param columnsToRead
-   * @return
+   * @return The {@link org.apache.drill.exec.store.easy.json.JSONRecordReader} corresponding to each given input path.
    */
   public static Iterator<RecordReader> getJsonReadersFromInputFiles(DrillFileSystem fs, List<String> inputPaths, FragmentContext fragContext, List<SchemaPath> columnsToRead) {
     List<RecordReader> readers = new ArrayList<>();