fix(server): remove extra blank lines (#2459)

* remove extra blank lines in api

* remove extra blank lines in core

* remove extra blank lines in scylladb
diff --git a/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/filter/DecompressInterceptor.java b/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/filter/DecompressInterceptor.java
index af8615a..488dd50 100644
--- a/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/filter/DecompressInterceptor.java
+++ b/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/filter/DecompressInterceptor.java
@@ -47,7 +47,6 @@
         return context.proceed();
     }
 
-
     @NameBinding
     @Retention(RetentionPolicy.RUNTIME)
     public @interface Decompress {
diff --git a/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/metrics/MetricsAPI.java b/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/metrics/MetricsAPI.java
index 4682c35..b0ca684 100644
--- a/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/metrics/MetricsAPI.java
+++ b/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/metrics/MetricsAPI.java
@@ -362,7 +362,6 @@
             Counter successCounter = reporter.counters().get(
                     joinWithSlash(metricsName, METRICS_PATH_SUCCESS_COUNTER));
 
-
             Histogram histogram = entry.getValue();
             Map<String, Object> entryMetricsMap = new HashMap<>();
             entryMetricsMap.put(MetricsKeys.MAX_RESPONSE_TIME.name(),
diff --git a/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/traversers/CustomizedCrosspointsAPI.java b/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/traversers/CustomizedCrosspointsAPI.java
index 03ebb82..8af4969 100644
--- a/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/traversers/CustomizedCrosspointsAPI.java
+++ b/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/api/traversers/CustomizedCrosspointsAPI.java
@@ -114,7 +114,6 @@
         measure.addIterCount(traverser.vertexIterCounter.get(),
                              traverser.edgeIterCounter.get());
 
-
         Iterator<?> iterVertex;
         Set<Id> vertexIds = new HashSet<>();
         if (request.withPath) {
diff --git a/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/core/GraphManager.java b/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/core/GraphManager.java
index 1830d81..cdd3184 100644
--- a/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/core/GraphManager.java
+++ b/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/core/GraphManager.java
@@ -347,7 +347,6 @@
         return this.authenticator;
     }
 
-
     private void closeTx(final Set<String> graphSourceNamesToCloseTxOn,
                          final Transaction.Status tx) {
         final Set<Graph> graphsToCloseTxOn = new HashSet<>();
diff --git a/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/metrics/MetricsUtil.java b/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/metrics/MetricsUtil.java
index 82f502e..47f28b4 100644
--- a/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/metrics/MetricsUtil.java
+++ b/hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/metrics/MetricsUtil.java
@@ -63,7 +63,6 @@
     public static final String RIGHT_NAME_STR = ",} ";
     public static final String PROM_HELP_NAME = "hugegraph_info";
 
-
     public static <T> Gauge<T> registerGauge(Class<?> clazz, String name,
                                              Gauge<T> gauge) {
         return REGISTRY.register(MetricRegistry.name(clazz, name), gauge);
diff --git a/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/job/algorithm/comm/KCoreAlgorithm.java b/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/job/algorithm/comm/KCoreAlgorithm.java
index e51aa27..eb334e5 100644
--- a/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/job/algorithm/comm/KCoreAlgorithm.java
+++ b/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/job/algorithm/comm/KCoreAlgorithm.java
@@ -190,7 +190,6 @@
             return extractKcore(map, k);
         }
 
-
         @SuppressWarnings("unchecked")
         private static Set<Id> extractKcore(SimilarsMap similarsMap, int k) {
             assert similarsMap.size() == 1;
diff --git a/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/masterelection/StandardClusterRoleStore.java b/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/masterelection/StandardClusterRoleStore.java
index a235fa1..4885410 100644
--- a/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/masterelection/StandardClusterRoleStore.java
+++ b/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/masterelection/StandardClusterRoleStore.java
@@ -176,7 +176,6 @@
         public static final String TYPE = Graph.Hidden.hide("role_type");
     }
 
-
     public static final class Schema extends SchemaDefine {
 
         public Schema(HugeGraphParams graph) {
diff --git a/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/security/HugeSecurityManager.java b/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/security/HugeSecurityManager.java
index 7c4f33c..5e2dc76 100644
--- a/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/security/HugeSecurityManager.java
+++ b/hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/security/HugeSecurityManager.java
@@ -48,7 +48,6 @@
     // TODO: add "suppressAccessChecks"
     private static final Set<String> DENIED_PERMISSIONS = ImmutableSet.of("setSecurityManager");
 
-
     private static final Set<String> ACCEPT_CLASS_LOADERS = ImmutableSet.of(
             "groovy.lang.GroovyClassLoader",
             "sun.reflect.DelegatingClassLoader",
diff --git a/hugegraph-server/hugegraph-scylladb/src/main/java/org/apache/hugegraph/backend/store/scylladb/ScyllaDBTablesWithMV.java b/hugegraph-server/hugegraph-scylladb/src/main/java/org/apache/hugegraph/backend/store/scylladb/ScyllaDBTablesWithMV.java
index 9846a18..4d0500a 100644
--- a/hugegraph-server/hugegraph-scylladb/src/main/java/org/apache/hugegraph/backend/store/scylladb/ScyllaDBTablesWithMV.java
+++ b/hugegraph-server/hugegraph-scylladb/src/main/java/org/apache/hugegraph/backend/store/scylladb/ScyllaDBTablesWithMV.java
@@ -221,7 +221,6 @@
             super.dropTable(session);
         }
 
-
         /**
          * Query data from label index table if just want to query by label
          */