diff --git a/common/src/main/java/com/taobao/arthas/common/ExecutingCommand.java b/common/src/main/java/com/taobao/arthas/common/ExecutingCommand.java
index 3bf1c20ceeb..fea80ff1e9a 100644
--- a/common/src/main/java/com/taobao/arthas/common/ExecutingCommand.java
+++ b/common/src/main/java/com/taobao/arthas/common/ExecutingCommand.java
@@ -44,11 +44,7 @@ public static List<String> runNative(String[] cmdToRunWithArgs) {
         Process p = null;
         try {
             p = Runtime.getRuntime().exec(cmdToRunWithArgs);
-        } catch (SecurityException e) {
-            AnsiLog.trace("Couldn't run command {}:", Arrays.toString(cmdToRunWithArgs));
-            AnsiLog.trace(e);
-            return new ArrayList<String>(0);
-        } catch (IOException e) {
+        } catch (SecurityException | IOException e) {
             AnsiLog.trace("Couldn't run command {}:", Arrays.toString(cmdToRunWithArgs));
             AnsiLog.trace(e);
             return new ArrayList<String>(0);
diff --git a/core/src/main/java/com/taobao/arthas/core/command/basic1000/JFRCommand.java b/core/src/main/java/com/taobao/arthas/core/command/basic1000/JFRCommand.java
index f615cbf9fd9..cba0b3cfaae 100644
--- a/core/src/main/java/com/taobao/arthas/core/command/basic1000/JFRCommand.java
+++ b/core/src/main/java/com/taobao/arthas/core/command/basic1000/JFRCommand.java
@@ -59,7 +59,7 @@ public class JFRCommand extends AnnotatedCommand {
     private JFRModel result = new JFRModel();
     private static Map<Long, Recording> recordings = new ConcurrentHashMap<Long, Recording>();
 
-    @Argument(index = 0, argName = "cmd", required = true)
+    @Argument(index = 0, argName = "cmd")
     @Description("command name (start status stop dump)")
     public void setCmd(String cmd) {
         this.cmd = cmd;
@@ -209,7 +209,7 @@ public void process(CommandProcess process) {
                 }
             }
 
-            if (isDumpOnExit() != false) {
+            if (isDumpOnExit()) {
                 r.setDumpOnExit(isDumpOnExit().booleanValue());
             }
 
@@ -256,6 +256,7 @@ public void process(CommandProcess process) {
                 Recording r = recordings.get(getRecording());
                 if (r == null) {
                     process.end(-1, "recording not exit");
+                    return;
                 }
                 printRecording(r);
             } else {// list all recordings
@@ -308,6 +309,7 @@ public void process(CommandProcess process) {
                 Recording r = recordings.remove(getRecording());
                 if (r == null) {
                     process.end(-1, "recording not exit");
+                    return;
                 }
                 if ("CLOSED".equals(r.getState().toString()) || "STOPPED".equals(r.getState().toString())) {
                     process.end(-1, "Failed to stop recording, state can not be closed/stopped");
diff --git a/core/src/main/java/com/taobao/arthas/core/command/basic1000/KeymapCommand.java b/core/src/main/java/com/taobao/arthas/core/command/basic1000/KeymapCommand.java
index 0d19640ef0c..727fc65db66 100644
--- a/core/src/main/java/com/taobao/arthas/core/command/basic1000/KeymapCommand.java
+++ b/core/src/main/java/com/taobao/arthas/core/command/basic1000/KeymapCommand.java
@@ -51,7 +51,7 @@ public void process(CommandProcess process) {
             String line;
             while ((line = br.readLine()) != null) {
                 line = line.trim();
-                if (line.startsWith("#") || "".equals(line)) {
+                if (line.isEmpty() || line.startsWith("#")) {
                     continue;
                 }
                 String[] strings = line.split(":");
diff --git a/core/src/main/java/com/taobao/arthas/core/command/klass100/OgnlCommand.java b/core/src/main/java/com/taobao/arthas/core/command/klass100/OgnlCommand.java
index b2dd6125dcd..7a8ccc070cc 100644
--- a/core/src/main/java/com/taobao/arthas/core/command/klass100/OgnlCommand.java
+++ b/core/src/main/java/com/taobao/arthas/core/command/klass100/OgnlCommand.java
@@ -46,7 +46,7 @@ public class OgnlCommand extends AnnotatedCommand {
     private String classLoaderClass;
     private int expand = 1;
 
-    @Argument(argName = "express", index = 0, required = true)
+    @Argument(argName = "express", index = 0)
     @Description("The ognl expression.")
     public void setExpress(String express) {
         this.express = express;