diff --git a/.github/ISSUE_TEMPLATE/bug_report.yml b/.github/ISSUE_TEMPLATE/bug_report.yml
index 8445d0a5..685c72de 100644
--- a/.github/ISSUE_TEMPLATE/bug_report.yml
+++ b/.github/ISSUE_TEMPLATE/bug_report.yml
@@ -28,7 +28,7 @@ body:
       options:
         - exception / error (异常报错)
         - logic (逻辑设计问题)
-        - performence (性能下降)
+        - performance (性能下降)
         - others (please edit later)
   
   - type: checkboxes
diff --git a/.github/ISSUE_TEMPLATE/question_ask.yml b/.github/ISSUE_TEMPLATE/question_ask.yml
index 9724e66c..6fb2d4eb 100644
--- a/.github/ISSUE_TEMPLATE/question_ask.yml
+++ b/.github/ISSUE_TEMPLATE/question_ask.yml
@@ -25,7 +25,7 @@ body:
       label: Problem Type (问题类型)
       options:
         - struct / logic (架构 / 逻辑设计问题)
-        - performence (性能优化)
+        - performance (性能优化)
         - exception / error (异常报错)
         - others (please edit later)
   
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/concurrent/KeyLock.java b/hugegraph-common/src/main/java/org/apache/hugegraph/concurrent/KeyLock.java
index eda012b8..351f50cf 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/concurrent/KeyLock.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/concurrent/KeyLock.java
@@ -88,7 +88,7 @@ public final List<Lock> lockAll(Object... keys) {
             Lock lock = this.locks.get(key);
             locks.add(lock);
         }
-        Collections.sort(locks, (a, b) -> {
+        locks.sort((a, b) -> {
             int diff = a.hashCode() - b.hashCode();
             if (diff == 0 && a != b) {
                 diff = this.indexOf(a) - this.indexOf(b);
@@ -96,8 +96,8 @@ public final List<Lock> lockAll(Object... keys) {
             }
             return diff;
         });
-        for (int i = 0; i < locks.size(); i++) {
-            locks.get(i).lock();
+        for (Lock lock : locks) {
+            lock.lock();
         }
         return Collections.unmodifiableList(locks);
     }
@@ -125,8 +125,8 @@ public List<Lock> lockAll(Object key1, Object key2) {
                            ImmutableList.of(lock2, lock1) :
                            ImmutableList.of(lock1, lock2);
 
-        for (int i = 0; i < locks.size(); i++) {
-            locks.get(i).lock();
+        for (Lock lock : locks) {
+            lock.lock();
         }
 
         return locks;
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/concurrent/PausableScheduledThreadPool.java b/hugegraph-common/src/main/java/org/apache/hugegraph/concurrent/PausableScheduledThreadPool.java
index e5dba9fe..ddfc8b72 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/concurrent/PausableScheduledThreadPool.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/concurrent/PausableScheduledThreadPool.java
@@ -28,8 +28,7 @@
 
 public class PausableScheduledThreadPool extends ScheduledThreadPoolExecutor {
 
-    private static final Logger LOG = Log.logger(
-                                      PausableScheduledThreadPool.class);
+    private static final Logger LOG = Log.logger(PausableScheduledThreadPool.class);
 
     private volatile boolean paused = false;
 
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/config/OptionChecker.java b/hugegraph-common/src/main/java/org/apache/hugegraph/config/OptionChecker.java
index 551fe93c..8676702a 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/config/OptionChecker.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/config/OptionChecker.java
@@ -21,6 +21,7 @@
 
 import java.lang.reflect.Array;
 import java.util.Arrays;
+import java.util.HashSet;
 import java.util.List;
 
 import javax.annotation.Nullable;
@@ -32,88 +33,55 @@
 public final class OptionChecker {
 
     public static <O> Predicate<O> disallowEmpty() {
-        return new Predicate<O>() {
-            @Override
-            public boolean apply(@Nullable O o) {
-                if (o == null) {
-                    return false;
-                }
-                if (o instanceof String) {
-                    return StringUtils.isNotBlank((String) o);
-                }
-                if (o.getClass().isArray() && (Array.getLength(o) == 0)) {
-                    return false;
-                }
-                if (o instanceof Iterable &&
-                    !((Iterable<?>) o).iterator().hasNext()) {
-                    return false;
-                }
-                return true;
+        return o -> {
+            if (o == null) {
+                return false;
             }
+            if (o instanceof String) {
+                return StringUtils.isNotBlank((String) o);
+            }
+            if (o.getClass().isArray() && (Array.getLength(o) == 0)) {
+                return false;
+            }
+            return !(o instanceof Iterable) || ((Iterable<?>) o).iterator().hasNext();
         };
     }
 
     @SuppressWarnings("unchecked")
     public static <O> Predicate<O> allowValues(O... values) {
-        return new Predicate<O>() {
-            @Override
-            public boolean apply(@Nullable O o) {
-                return o != null && Arrays.asList(values).contains(o);
-            }
-        };
+        return o -> o != null && Arrays.asList(values).contains(o);
     }
 
     @SuppressWarnings("unchecked")
     public static <O> Predicate<List<O>> inValues(O... values) {
-        return new Predicate<List<O>>() {
-            @Override
-            public boolean apply(@Nullable List<O> o) {
-                return o != null && Arrays.asList(values).containsAll(o);
-            }
-        };
+        return o -> o != null && new HashSet<>(Arrays.asList(values)).containsAll(o);
     }
 
     public static <N extends Number> Predicate<N> positiveInt() {
-        return new Predicate<N>() {
-            @Override
-            public boolean apply(@Nullable N number) {
-                return number != null && number.longValue() > 0;
-            }
-        };
+        return number -> number != null && number.longValue() > 0;
     }
 
     public static <N extends Number> Predicate<N> nonNegativeInt() {
-        return new Predicate<N>() {
-            @Override
-            public boolean apply(@Nullable N number) {
-                return number != null && number.longValue() >= 0;
-            }
-        };
+        return number -> number != null && number.longValue() >= 0;
     }
 
     public static <N extends Number> Predicate<N> rangeInt(N min, N max) {
-        return new Predicate<N>() {
-            @Override
-            public boolean apply(@Nullable N number) {
-                if (number == null) {
-                    return false;
-                }
-                long value = number.longValue();
-                return value >= min.longValue() && value <= max.longValue();
+        return number -> {
+            if (number == null) {
+                return false;
             }
+            long value = number.longValue();
+            return value >= min.longValue() && value <= max.longValue();
         };
     }
 
     public static <N extends Number> Predicate<N> rangeDouble(N min, N max) {
-        return new Predicate<N>() {
-            @Override
-            public boolean apply(@Nullable N number) {
-                if (number == null) {
-                    return false;
-                }
-                double value = number.doubleValue();
-                return value >= min.doubleValue() && value <= max.doubleValue();
+        return number -> {
+            if (number == null) {
+                return false;
             }
+            double value = number.doubleValue();
+            return value >= min.doubleValue() && value <= max.doubleValue();
         };
     }
 }
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/date/SafeDateFormat.java b/hugegraph-common/src/main/java/org/apache/hugegraph/date/SafeDateFormat.java
index 0deba51e..9f9a665f 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/date/SafeDateFormat.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/date/SafeDateFormat.java
@@ -48,7 +48,7 @@ public synchronized void setTimeZone(String zoneId) {
         this.formatter = this.formatter.withZone(zone);
     }
 
-    public TimeZone getTimeZome() {
+    public TimeZone getTimeZone() {
         return this.formatter.getZone().toTimeZone();
     }
 
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/event/EventHub.java b/hugegraph-common/src/main/java/org/apache/hugegraph/event/EventHub.java
index 0e426fcb..2db83474 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/event/EventHub.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/event/EventHub.java
@@ -159,8 +159,8 @@ public Future<Integer> notify(String event, @Nullable Object... args) {
                 try {
                     all.next().event(ev);
                     count++;
-                } catch (Throwable ignored) {
-                    LOG.warn("Failed to handle event: {}", ev, ignored);
+                } catch (Throwable e) {
+                    LOG.warn("Failed to handle event: {}", ev, e);
                 }
             }
             return count;
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/event/EventListener.java b/hugegraph-common/src/main/java/org/apache/hugegraph/event/EventListener.java
index a0deb4c0..3810926f 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/event/EventListener.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/event/EventListener.java
@@ -25,5 +25,5 @@ public interface EventListener extends java.util.EventListener {
      * @param event object
      * @return event result
      */
-    public Object event(Event event);
+    Object event(Event event);
 }
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/func/TriFunction.java b/hugegraph-common/src/main/java/org/apache/hugegraph/func/TriFunction.java
index b381d42e..d84c26f3 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/func/TriFunction.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/func/TriFunction.java
@@ -20,5 +20,6 @@
 package org.apache.hugegraph.func;
 
 public interface TriFunction <T1, T2, T3, R> {
-    public R apply(T1 v1, T2 v2, T3 v3);
+
+    R apply(T1 v1, T2 v2, T3 v3);
 }
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/iterator/ExtendableIterator.java b/hugegraph-common/src/main/java/org/apache/hugegraph/iterator/ExtendableIterator.java
index d4e690f8..a07f3e47 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/iterator/ExtendableIterator.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/iterator/ExtendableIterator.java
@@ -82,7 +82,7 @@ protected boolean fetch() {
             return true;
         }
 
-        Iterator<T> first = null;
+        Iterator<T> first;
         while ((first = this.itors.peekFirst()) != null && !first.hasNext()) {
             if (first == this.itors.peekLast() && this.itors.size() == 1) {
                 this.currentIterator = first;
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/iterator/Metadatable.java b/hugegraph-common/src/main/java/org/apache/hugegraph/iterator/Metadatable.java
index 2f7d81f3..777e4680 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/iterator/Metadatable.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/iterator/Metadatable.java
@@ -21,5 +21,5 @@
 
 public interface Metadatable {
 
-    public Object metadata(String meta, Object... args);
+    Object metadata(String meta, Object... args);
 }
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/license/LicenseManager.java b/hugegraph-common/src/main/java/org/apache/hugegraph/license/LicenseManager.java
index 73788999..f87b9ebb 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/license/LicenseManager.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/license/LicenseManager.java
@@ -21,14 +21,14 @@
 
 public interface LicenseManager {
 
-    public LicenseParams installLicense() throws Exception;
+    LicenseParams installLicense() throws Exception;
 
-    public void uninstallLicense() throws Exception;
+    void uninstallLicense() throws Exception;
 
-    public LicenseParams verifyLicense() throws Exception;
+    LicenseParams verifyLicense() throws Exception;
 
-    public interface VerifyCallback {
+    interface VerifyCallback {
 
-        public void onVerifyLicense(LicenseParams params) throws Exception;
+        void onVerifyLicense(LicenseParams params) throws Exception;
     }
 }
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/perf/LightStopwatch.java b/hugegraph-common/src/main/java/org/apache/hugegraph/perf/LightStopwatch.java
index 1f63de73..ca81082e 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/perf/LightStopwatch.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/perf/LightStopwatch.java
@@ -135,8 +135,7 @@ public long totalChildrenWasted() {
     @Override
     public void fillChildrenTotal(List<Stopwatch> children) {
         // Fill total times of children
-        this.totalChildrenTimes = children.stream().mapToLong(
-                                  c -> c.totalTimes()).sum();
+        this.totalChildrenTimes = children.stream().mapToLong(Stopwatch::totalTimes).sum();
     }
 
     @Override
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/perf/NormalStopwatch.java b/hugegraph-common/src/main/java/org/apache/hugegraph/perf/NormalStopwatch.java
index 8b8aa069..c595a343 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/perf/NormalStopwatch.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/perf/NormalStopwatch.java
@@ -184,11 +184,9 @@ public long totalChildrenWasted() {
     @Override
     public void fillChildrenTotal(List<Stopwatch> children) {
         // Fill total wasted cost of children
-        this.totalChildrenWasted = children.stream().mapToLong(
-                                   c -> c.totalWasted()).sum();
+        this.totalChildrenWasted = children.stream().mapToLong(Stopwatch::totalWasted).sum();
         // Fill total times of children
-        this.totalChildrenTimes = children.stream().mapToLong(
-                                  c -> c.totalTimes()).sum();
+        this.totalChildrenTimes = children.stream().mapToLong(Stopwatch::totalTimes).sum();
     }
 
     @Override
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/perf/PerfUtil.java b/hugegraph-common/src/main/java/org/apache/hugegraph/perf/PerfUtil.java
index 62bd713e..1918f269 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/perf/PerfUtil.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/perf/PerfUtil.java
@@ -681,8 +681,8 @@ public void clear() {
 
     @Retention(RetentionPolicy.RUNTIME)
     @Target({ ElementType.METHOD, ElementType.CONSTRUCTOR })
-    public static @interface Watched {
-        public String value() default "";
-        public String prefix() default "";
+    public @interface Watched {
+        String value() default "";
+        String prefix() default "";
     }
 }
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/perf/Stopwatch.java b/hugegraph-common/src/main/java/org/apache/hugegraph/perf/Stopwatch.java
index 074869d9..9d095c92 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/perf/Stopwatch.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/perf/Stopwatch.java
@@ -23,40 +23,40 @@
 
 public interface Stopwatch extends Cloneable {
 
-    public Path id();
-    public String name();
-    public Path parent();
+    Path id();
+    String name();
+    Path parent();
 
-    public void startTime(long startTime);
-    public void endTime(long startTime);
+    void startTime(long startTime);
+    void endTime(long startTime);
 
-    public void lastStartTime(long startTime);
+    void lastStartTime(long startTime);
 
-    public long times();
-    public long totalTimes();
-    public long totalChildrenTimes();
+    long times();
+    long totalTimes();
+    long totalChildrenTimes();
 
-    public long totalCost();
-    public void totalCost(long otherCost);
+    long totalCost();
+    void totalCost(long otherCost);
 
-    public long minCost();
-    public long maxCost();
+    long minCost();
+    long maxCost();
 
-    public long totalWasted();
-    public long totalSelfWasted();
-    public long totalChildrenWasted();
+    long totalWasted();
+    long totalSelfWasted();
+    long totalChildrenWasted();
 
-    public void fillChildrenTotal(List<Stopwatch> children);
+    void fillChildrenTotal(List<Stopwatch> children);
 
-    public Stopwatch copy();
+    Stopwatch copy();
 
-    public Stopwatch child(String name);
-    public Stopwatch child(String name, Stopwatch watch);
+    Stopwatch child(String name);
+    Stopwatch child(String name, Stopwatch watch);
 
-    public boolean empty();
-    public void clear();
+    boolean empty();
+    void clear();
 
-    public default String toJson() {
+    default String toJson() {
         int len = 200 + this.name().length() + this.parent().length();
         StringBuilder sb = new StringBuilder(len);
         sb.append("{");
@@ -75,14 +75,14 @@ public default String toJson() {
         return sb.toString();
     }
 
-    public static Path id(Path parent, String name) {
+    static Path id(Path parent, String name) {
         if (parent == Path.EMPTY && name == Path.ROOT_NAME) {
             return Path.EMPTY;
         }
         return new Path(parent, name);
     }
 
-    public static final class Path implements Comparable<Path> {
+    final class Path implements Comparable<Path> {
 
         public static final String ROOT_NAME = "root";
         public static final Path EMPTY = new Path("");
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/rest/AbstractRestClient.java b/hugegraph-common/src/main/java/org/apache/hugegraph/rest/AbstractRestClient.java
index bf156b8e..276a8fe0 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/rest/AbstractRestClient.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/rest/AbstractRestClient.java
@@ -435,11 +435,11 @@ private static PoolingHttpClientConnectionManager connectionManager(
                                                       String url,
                                                       ClientConfig conf) {
         String protocol = (String) conf.getProperty("protocol");
-        if (protocol == null || protocol.equals("http")) {
+        if (protocol == null || "http".equals(protocol)) {
             return new PoolingHttpClientConnectionManager(TTL, TimeUnit.HOURS);
         }
 
-        assert protocol.equals("https");
+        assert "https".equals(protocol);
         String trustStoreFile = (String) conf.getProperty("trustStoreFile");
         E.checkArgument(trustStoreFile != null && !trustStoreFile.isEmpty(),
                         "The trust store file must be set when use https");
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/rest/RestClient.java b/hugegraph-common/src/main/java/org/apache/hugegraph/rest/RestClient.java
index 3e095d53..06347b3b 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/rest/RestClient.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/rest/RestClient.java
@@ -24,31 +24,45 @@
 import jakarta.ws.rs.core.MultivaluedMap;
 
 public interface RestClient {
+    /**
+     * Post method
+     */
+    RestResult post(String path, Object object);
 
-    public RestResult post(String path, Object object);
-    public RestResult post(String path, Object object,
-                           MultivaluedMap<String, Object> headers);
-    public RestResult post(String path, Object object,
-                           Map<String, Object> params);
-    public RestResult post(String path, Object object,
-                           MultivaluedMap<String, Object> headers,
-                           Map<String, Object> params);
-
-    public RestResult put(String path, String id, Object object);
-    public RestResult put(String path, String id, Object object,
-                          MultivaluedMap<String, Object> headers);
-    public RestResult put(String path, String id, Object object,
-                          Map<String, Object> params);
-    public RestResult put(String path, String id, Object object,
-                          MultivaluedMap<String, Object> headers,
-                          Map<String, Object> params);
-
-    public RestResult get(String path);
-    public RestResult get(String path, Map<String, Object> params);
-    public RestResult get(String path, String id);
-
-    public RestResult delete(String path, Map<String, Object> params);
-    public RestResult delete(String path, String id);
-
-    public void close();
+    RestResult post(String path, Object object, MultivaluedMap<String, Object> headers);
+
+    RestResult post(String path, Object object, Map<String, Object> params);
+
+    RestResult post(String path, Object object, MultivaluedMap<String, Object> headers,
+                    Map<String, Object> params);
+
+    /**
+     * Put method
+     */
+    RestResult put(String path, String id, Object object);
+
+    RestResult put(String path, String id, Object object, MultivaluedMap<String, Object> headers);
+
+    RestResult put(String path, String id, Object object, Map<String, Object> params);
+
+    RestResult put(String path, String id, Object object, MultivaluedMap<String, Object> headers,
+                   Map<String, Object> params);
+
+    /**
+     * Get method
+     */
+    RestResult get(String path);
+
+    RestResult get(String path, Map<String, Object> params);
+
+    RestResult get(String path, String id);
+
+    /**
+     * Delete method
+     */
+    RestResult delete(String path, Map<String, Object> params);
+
+    RestResult delete(String path, String id);
+
+    void close();
 }
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/testutil/Assert.java b/hugegraph-common/src/main/java/org/apache/hugegraph/testutil/Assert.java
index 284c5721..519d2053 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/testutil/Assert.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/testutil/Assert.java
@@ -42,9 +42,7 @@ public interface ThrowableConsumer<T> {
     public static void assertThrows(Class<? extends Throwable> throwable,
                                     ThrowableRunnable runnable) {
         CompletableFuture<?> future = assertThrowsFuture(throwable, runnable);
-        future.thenAccept(e -> {
-            System.err.println(e);
-        });
+        future.thenAccept(System.err::println);
     }
 
     public static void assertThrows(Class<? extends Throwable> throwable,
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/util/CheckSocket.java b/hugegraph-common/src/main/java/org/apache/hugegraph/util/CheckSocket.java
index 99243882..96d83e38 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/util/CheckSocket.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/util/CheckSocket.java
@@ -47,8 +47,8 @@ public static void main(String[] args) {
                                   Integer.parseInt(args[1]));
             s.close();
             System.exit(0);
-        } catch (IOException ignored) {
-            System.err.println(ignored.toString());
+        } catch (IOException e) {
+            System.err.println(e);
             System.exit(E_FAILED);
         }
     }
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/util/CollectionUtil.java b/hugegraph-common/src/main/java/org/apache/hugegraph/util/CollectionUtil.java
index c1f3404e..6e04858b 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/util/CollectionUtil.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/util/CollectionUtil.java
@@ -150,7 +150,7 @@ public static <T> Collection<T> intersect(Collection<T> first,
         E.checkNotNull(first, "first");
         E.checkNotNull(second, "second");
 
-        HashSet<T> results = null;
+        HashSet<T> results;
         if (first instanceof HashSet) {
             @SuppressWarnings("unchecked")
             HashSet<T> clone = (HashSet<T>) ((HashSet<T>) first).clone();
@@ -303,7 +303,7 @@ public static <T> List<List<T>> cnm(List<T> all, int n, int m) {
      * @param n m of C(n, m)
      * @param m n of C(n, m)
      * @return true if matched any kind of items combination else false, the
-     * callback can always return false if want to traverse all combinations
+     * callback can always return false if you want to traverse all combinations
      */
     public static <T> boolean cnm(List<T> all, int n, int m,
                                   Function<List<T>, Boolean> callback) {
@@ -317,9 +317,9 @@ public static <T> boolean cnm(List<T> all, int n, int m,
      * @param n n of C(n, m)
      * @param m m of C(n, m)
      * @param current current position in list
-     * @param selected list to contains selected items
+     * @param selected list to contain selected items
      * @return true if matched any kind of items combination else false, the
-     * callback can always return false if want to traverse all combinations
+     * callback can always return false if you want to traverse all combinations
      */
     private static <T> boolean cnm(List<T> all, int n, int m,
                                    int current, List<T> selected,
@@ -360,11 +360,7 @@ private static <T> boolean cnm(List<T> all, int n, int m,
         // Not select current item, pop it and continue to select C(m-1, n)
         selected.remove(index);
         assert selected.size() == index : selected;
-        if (cnm(all, n - 1, m, current, selected, callback)) {
-            return true;
-        }
-
-        return false;
+        return cnm(all, n - 1, m, current, selected, callback);
     }
 
     /**
@@ -399,7 +395,7 @@ public static <T> List<List<T>> anm(List<T> all, int n, int m) {
      * @param n m of A(n, m)
      * @param m n of A(n, m)
      * @return true if matched any kind of items combination else false, the
-     * callback can always return false if want to traverse all combinations
+     * callback can always return false if you want to traverse all combinations
      */
     public static <T> boolean anm(List<T> all, int n, int m,
                                   Function<List<T>, Boolean> callback) {
@@ -412,9 +408,9 @@ public static <T> boolean anm(List<T> all, int n, int m,
      * @param all list to contain all items for combination
      * @param n m of A(n, m)
      * @param m n of A(n, m)
-     * @param selected list to contains selected items
+     * @param selected list to contain selected items
      * @return true if matched any kind of items combination else false, the
-     * callback can always return false if want to traverse all combinations
+     * callback can always return false if you want to traverse all combinations
      */
     private static <T> boolean anm(List<T> all, int n, int m,
                                    List<Integer> selected,
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/util/NumericUtil.java b/hugegraph-common/src/main/java/org/apache/hugegraph/util/NumericUtil.java
index d9dd1904..f567a895 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/util/NumericUtil.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/util/NumericUtil.java
@@ -40,7 +40,7 @@ private NumericUtil() {
      * <code>long</code>. The value is converted by getting their IEEE 754
      * floating-point &quot;double format&quot; bit layout and then some bits
      * are swapped, to be able to compare the result as long. By this the
-     * precision is not reduced, but the value can easily used as a long. The
+     * precision is not reduced, but the value can be easily used as a long. The
      * sort order (including {@link Double#NaN}) is defined by
      * {@link Double#compareTo}; {@code NaN} is greater than positive infinity.
      * @param value input double value
@@ -66,7 +66,7 @@ public static double sortableLongToDouble(long value) {
      * <code>int</code>. The value is converted by getting their IEEE 754
      * floating-point &quot;float format&quot; bit layout and then some bits are
      * swapped, to be able to compare the result as int. By this the precision
-     * is not reduced, but the value can easily used as an int. The sort order
+     * is not reduced, but the value can be easily used as an int. The sort order
      * (including {@link Float#NaN}) is defined by {@link Float#compareTo};
      * {@code NaN} is greater than positive infinity.
      * @param value input float value
@@ -100,7 +100,7 @@ public static long sortableDoubleBits(long bits) {
     /**
      * Converts IEEE 754 representation of a float to sortable order (or back to
      * the original)
-     * @param bits The int format of an float value
+     * @param bits The int format of a float value
      * @return The sortable int value
      */
     public static int sortableFloatBits(int bits) {
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/util/UnitUtil.java b/hugegraph-common/src/main/java/org/apache/hugegraph/util/UnitUtil.java
index e21ed9e6..138fed9c 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/util/UnitUtil.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/util/UnitUtil.java
@@ -156,7 +156,7 @@ public static long timestampFromReadableString(String valueWithUnit) {
         } else {
             // Not exists days
             int msPos = formatDuration.indexOf("MS");
-            // If contains ms, rmove the ms part
+            // If contains ms, remove the ms part
             if (msPos >= 0) {
                 int sPos = formatDuration.indexOf("S");
                 if (0 <= sPos && sPos < msPos) {
diff --git a/hugegraph-common/src/main/java/org/apache/hugegraph/util/VersionUtil.java b/hugegraph-common/src/main/java/org/apache/hugegraph/util/VersionUtil.java
index 57c9eb7c..4bd76f77 100644
--- a/hugegraph-common/src/main/java/org/apache/hugegraph/util/VersionUtil.java
+++ b/hugegraph-common/src/main/java/org/apache/hugegraph/util/VersionUtil.java
@@ -94,7 +94,7 @@ public static String getImplementationVersion(Class<?> clazz) {
     public static String getImplementationVersion(String manifestPath) {
         manifestPath += "/META-INF/MANIFEST.MF";
 
-        Manifest manifest = null;
+        Manifest manifest;
         try {
             manifest = new Manifest(new URL(manifestPath).openStream());
         } catch (IOException ignored) {
diff --git a/hugegraph-common/src/test/java/org/apache/hugegraph/unit/date/SafeDateFormatTest.java b/hugegraph-common/src/test/java/org/apache/hugegraph/unit/date/SafeDateFormatTest.java
index 6c9e89ed..68bad8c3 100644
--- a/hugegraph-common/src/test/java/org/apache/hugegraph/unit/date/SafeDateFormatTest.java
+++ b/hugegraph-common/src/test/java/org/apache/hugegraph/unit/date/SafeDateFormatTest.java
@@ -109,7 +109,7 @@ public void testTimeZone() throws ParseException {
         SafeDateFormat sdf = new SafeDateFormat("yyyy-MM-dd HH:mm:ss");
         sdf.setTimeZone("GMT+10");
 
-        Assert.assertEquals(df.getTimeZone(), sdf.getTimeZome());
+        Assert.assertEquals(df.getTimeZone(), sdf.getTimeZone());
         Assert.assertEquals(df.parse("2019-08-10 00:00:00"),
                             sdf.parse("2019-08-10 00:00:00"));
         Assert.assertEquals("2019-08-10 00:00:00",
@@ -118,7 +118,7 @@ public void testTimeZone() throws ParseException {
                             sdf.format(sdf.parse("2019-08-10 00:00:00")));
 
         sdf.setTimeZone("GMT+11");
-        Assert.assertNotEquals(df.getTimeZone(), sdf.getTimeZome());
+        Assert.assertNotEquals(df.getTimeZone(), sdf.getTimeZone());
         Assert.assertNotEquals(df.parse("2019-08-10 00:00:00"),
                                sdf.parse("2019-08-10 00:00:00"));
         Assert.assertEquals("2019-08-10 00:00:00",
diff --git a/hugegraph-rpc/src/main/java/org/apache/hugegraph/rpc/RpcServiceConfig4Client.java b/hugegraph-rpc/src/main/java/org/apache/hugegraph/rpc/RpcServiceConfig4Client.java
index 51b59c4a..333f0abc 100644
--- a/hugegraph-rpc/src/main/java/org/apache/hugegraph/rpc/RpcServiceConfig4Client.java
+++ b/hugegraph-rpc/src/main/java/org/apache/hugegraph/rpc/RpcServiceConfig4Client.java
@@ -21,17 +21,17 @@
 
 public interface RpcServiceConfig4Client {
 
-    public <T> T serviceProxy(String interfaceId);
+    <T> T serviceProxy(String interfaceId);
 
-    public <T> T serviceProxy(String graph, String interfaceId);
+    <T> T serviceProxy(String graph, String interfaceId);
 
-    public default <T> T serviceProxy(Class<T> clazz) {
+    default <T> T serviceProxy(Class<T> clazz) {
         return this.serviceProxy(clazz.getName());
     }
 
-    public default <T> T serviceProxy(String graph, Class<T> clazz) {
+    default <T> T serviceProxy(String graph, Class<T> clazz) {
         return this.serviceProxy(graph, clazz.getName());
     }
 
-    public void removeAllServiceProxy();
+    void removeAllServiceProxy();
 }
diff --git a/hugegraph-rpc/src/main/java/org/apache/hugegraph/rpc/RpcServiceConfig4Server.java b/hugegraph-rpc/src/main/java/org/apache/hugegraph/rpc/RpcServiceConfig4Server.java
index 9c0a0e51..03593504 100644
--- a/hugegraph-rpc/src/main/java/org/apache/hugegraph/rpc/RpcServiceConfig4Server.java
+++ b/hugegraph-rpc/src/main/java/org/apache/hugegraph/rpc/RpcServiceConfig4Server.java
@@ -21,12 +21,12 @@
 
 public interface RpcServiceConfig4Server {
 
-    public <T, S extends T> String addService(Class<T> clazz, S serviceImpl);
+    <T, S extends T> String addService(Class<T> clazz, S serviceImpl);
 
-    public <T, S extends T> String addService(String graph,
+    <T, S extends T> String addService(String graph,
                                               Class<T> clazz, S serviceImpl);
 
-    public void removeService(String serviceId);
+    void removeService(String serviceId);
 
-    public void removeAllService();
+    void removeAllService();
 }
diff --git a/hugegraph-rpc/src/test/java/org/apache/hugegraph/unit/ExceptionTest.java b/hugegraph-rpc/src/test/java/org/apache/hugegraph/unit/ExceptionTest.java
index 9ca812a5..c70d00b7 100644
--- a/hugegraph-rpc/src/test/java/org/apache/hugegraph/unit/ExceptionTest.java
+++ b/hugegraph-rpc/src/test/java/org/apache/hugegraph/unit/ExceptionTest.java
@@ -30,7 +30,7 @@ public class ExceptionTest {
     public void testExceptionWithMessage() {
         RpcException e = new RpcException("test");
         Assert.assertEquals("test", e.getMessage());
-        Assert.assertEquals(null, e.getCause());
+        Assert.assertNull(e.getCause());
     }
 
     @Test
@@ -45,7 +45,7 @@ public void testExceptionWithMessageAndCause() {
     public void testExceptionWithMessageAndArgs() {
         RpcException e = new RpcException("test %s", 168);
         Assert.assertEquals("test 168", e.getMessage());
-        Assert.assertEquals(null, e.getCause());
+        Assert.assertNull(e.getCause());
     }
 
     @Test
diff --git a/hugegraph-rpc/src/test/java/org/apache/hugegraph/unit/ServerClientTest.java b/hugegraph-rpc/src/test/java/org/apache/hugegraph/unit/ServerClientTest.java
index 590749e1..7f73a9af 100644
--- a/hugegraph-rpc/src/test/java/org/apache/hugegraph/unit/ServerClientTest.java
+++ b/hugegraph-rpc/src/test/java/org/apache/hugegraph/unit/ServerClientTest.java
@@ -682,9 +682,7 @@ public void testServerDisabled() {
         RpcServer rpcServerDisabled = new RpcServer(clientConf);
 
         Assert.assertFalse(rpcServerDisabled.enabled());
-        Assert.assertThrows(IllegalArgumentException.class, () -> {
-            rpcServerDisabled.config();
-        }, e -> {
+        Assert.assertThrows(IllegalArgumentException.class, rpcServerDisabled::config, e -> {
             Assert.assertContains("RpcServer is not enabled", e.getMessage());
         });
 
@@ -697,9 +695,7 @@ public void testClientDisabled() {
         RpcClientProvider rpcClientDisabled = new RpcClientProvider(serverConf);
 
         Assert.assertFalse(rpcClientDisabled.enabled());
-        Assert.assertThrows(IllegalArgumentException.class, () -> {
-            rpcClientDisabled.config();
-        }, e -> {
+        Assert.assertThrows(IllegalArgumentException.class, rpcClientDisabled::config, e -> {
             Assert.assertContains("RpcClient is not enabled", e.getMessage());
         });