Fix Checkstyle

Test Plan:
mvn clean site -DskipTests -Phadoop_2 -Ddependency.locations.enabled=false
mvn clean install -Phadoop_2 -Prelease
mvn clean install -Phadoop_1 -Prelease

Reviewers: dionysis.logothetis

Reviewed By: dionysis.logothetis

Differential Revision: https://reviews.facebook.net/D65499

giraph-block-app/src/main/java/org/apache/giraph/block_app/framework/api/BlockApiHandle.java

@@ -17,9 +17,6 @@
  */
 package org.apache.giraph.block_app.framework.api;
 
-import org.apache.giraph.block_app.framework.block.Block;
-import org.apache.giraph.block_app.framework.block.BlockWithApiHandle;
-
 import static com.google.common.base.Preconditions.checkNotNull;
 
 /**
@@ -30,8 +27,10 @@
  * Block Api interfaces, (ii) are not in the context of a Piece when defined,
  * and (iii) are in the context of a Piece when executed.
  *
- * To do this, as opposed to defining an application as a {@link Block}, define
- * your application as a {@link BlockWithApiHandle}.
+ * To do this, as opposed to defining an application as a
+ * {@link org.apache.giraph.block_app.framework.block.Block}, define
+ * your application as a
+ * {@link org.apache.giraph.block_app.framework.block.BlockWithApiHandle}.
  *
  * NOTE: Depending on the context in which this class is used, some of the
  * handles may not be set. For instance, the {@link masterApi} is not set when

giraph-core/src/main/java/org/apache/giraph/comm/flow_control/CreditBasedFlowControl.java

@@ -59,12 +59,13 @@
 /**
  * Representation of credit-based flow control policy. With this policy there
  * can be limited number of open requests from any worker x to any other worker
- * y. This number is called 'credit'. Let's denote this number by C{x->y}. This
- * implementation assumes that for a particular worker W, all values of C{x->W}
- * are the same. Let's denote this value by CR_W. CR_W may change due to other
- * reasons (e.g. memory pressure observed in an out-of-core mechanism). However,
- * CR_W is always in range [0, MAX_CR], where MAX_CR is a user-defined constant.
- * Note that MAX_CR should be representable by at most 14 bits.
+ * y. This number is called 'credit'. Let's denote this number by C{x->y}.
+ * This implementation assumes that for a particular worker W, all values of
+ * C{x->W} are the same. Let's denote this value by CR_W. CR_W may change
+ * due to other reasons (e.g. memory pressure observed in an out-of-core
+ * mechanism). However, CR_W is always in range [0, MAX_CR], where MAX_CR
+ * is a user-defined constant. Note that MAX_CR should be representable by
+ * at most 14 bits.
  *
  * In this implementation, the value of CR_W is announced to other workers along
  * with the ACK response envelope for all ACK response envelope going out of W.

giraph-core/src/main/java/org/apache/giraph/jython/JythonComputation.java

@@ -20,10 +20,8 @@
 import org.apache.giraph.conf.DefaultImmutableClassesGiraphConfigurable;
 import org.apache.giraph.edge.Edge;
 import org.apache.giraph.edge.OutEdges;
-import org.apache.giraph.graph.Computation;
 import org.apache.giraph.graph.GraphType;
 import org.apache.giraph.graph.Vertex;
-import org.apache.giraph.jython.wrappers.JythonWritableWrapper;
 import org.apache.giraph.worker.WorkerContext;
 import org.apache.hadoop.io.Writable;
 import org.apache.hadoop.io.WritableComparable;
@@ -35,16 +33,20 @@
 /**
  * Base class for writing computations in Jython.
  *
- * Note that this class DOES NOT implement {@link Computation}. This is because
- * we want to support passing in pure Jython types, and implementing the
- * {@link Computation} requires passing in {@link Writable}s. Calling such
- * methods from Jython would throw errors. So, instead, we have recreated the
- * methods with the same name here. In each method we check if the type is a
- * pure Jython value, and if so wrap it in the necessary
- * {@link JythonWritableWrapper}.
+ * Note that this class DOES NOT implement
+ * {@link org.apache.giraph.graph.Computation}.
+ * This is because we want to support passing in pure Jython types,
+ * and implementing the {@link org.apache.giraph.graph.Computation}
+ * requires passing in {@link Writable}s.
+ * Calling such methods from Jython would throw errors. So, instead,
+ * we have recreated the methods with the same name here. In each method
+ * we check if the type is a pure Jython value, and if so wrap it in
+ * the necessary
+ * {@link org.apache.giraph.jython.wrappers.JythonWritableWrapper}.
  *
  * This class works together with {@link JythonGiraphComputation} which takes
- * care of the {@link Computation} Giraph infrastructure side of things.
+ * care of the {@link org.apache.giraph.graph.Computation}
+ * Giraph infrastructure side of things.
  */
 public abstract class JythonComputation extends
     DefaultImmutableClassesGiraphConfigurable {

giraph-core/src/main/java/org/apache/giraph/jython/JythonGiraphComputation.java

@@ -18,7 +18,6 @@
 package org.apache.giraph.jython;
 
 import org.apache.giraph.graph.AbstractComputation;
-import org.apache.giraph.graph.Computation;
 import org.apache.giraph.graph.GraphType;
 import org.apache.giraph.graph.Language;
 import org.apache.giraph.graph.Vertex;
@@ -32,9 +31,10 @@
 import java.io.IOException;
 
 /**
- * The {@link Computation} class for using Jython with Giraph. This class
- * implements the Giraph necessary interfaces but it actually holds a reference
- * to the {@link JythonComputation} which does the real work.
+ * The {@link org.apache.giraph.graph.Computation} class for using
+ * Jython with Giraph. This class implements the Giraph necessary
+ * interfaces but it actually holds a reference to the
+ * {@link JythonComputation} which does the real work.
  *
  * The two classes are linked and together they allow us to coerce Jython types
  * to Writables.

giraph-core/src/main/java/org/apache/giraph/jython/factories/JythonOutgoingMessageValueFactory.java

@@ -17,13 +17,12 @@
  */
 package org.apache.giraph.jython.factories;
 
-import org.apache.giraph.factories.MessageValueFactory;
 import org.apache.giraph.jython.JythonOptions;
 import org.apache.hadoop.io.Writable;
 
 /**
- * {@link MessageValueFactory} that creates outgoing message values which are
- * Jython classes.
+ * {@link org.apache.giraph.factories.MessageValueFactory} that
+ * creates outgoing message values which are Jython classes.
  *
  * @param <M> Outgoing Message Value
  */

giraph-core/src/main/java/org/apache/giraph/metrics/GiraphMetricsRegistry.java

@@ -274,7 +274,8 @@ public Timer getTimer(String name, TimeUnit durationUnit, TimeUnit rateUnit) {
    * Get a Gauge that is already present in the MetricsRegistry
    *
    * @param name String name of Gauge
-   * @return Gauge<T> from MetricsRegistry
+   * @param <T> type of gauge
+   * @return Gauge, from MetricsRegistry
    */
   public <T> Gauge<T> getExistingGauge(String name) {
     Metric metric = registry.allMetrics().get(makeMetricName(name));

giraph-core/src/main/java/org/apache/giraph/reducers/ReduceOperation.java

@@ -17,7 +17,6 @@
  */
 package org.apache.giraph.reducers;
 
-import org.apache.giraph.master.AggregatorReduceOperation;
 import org.apache.hadoop.io.Writable;
 
 /**
@@ -27,7 +26,8 @@
  *
  * Object should be thread safe. Most frequently it should be
  * immutable object, so that functions can execute concurrently.
- * Rarely when object is mutable ({@link AggregatorReduceOperation}),
+ * Rarely when object is mutable
+ * ({@link org.apache.giraph.master.AggregatorReduceOperation}),
  * i.e. stores reusable object inside, accesses should be synchronized.
  *
  * @param <S> Single value type, objects passed on workers

giraph-core/src/main/java/org/apache/giraph/reducers/impl/MaxPairReducer.java

@@ -30,7 +30,8 @@
 
 
 /**
- * Aggregating PairWritable<L, R>, by taking pair with largest second value.
+ * Aggregating PairWritable<L, R>, by taking pair with
+ * largest second value.
  *
  * @param <L> Type of the left value
  * @param <R> Type of the right value