diff --git a/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/OSUtils.java b/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/OSUtils.java
index d7e6d23a88..acf3e310cc 100644
--- a/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/OSUtils.java
+++ b/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/OSUtils.java
@@ -26,7 +26,7 @@ public class OSUtils {
         throw new UnsupportedOperationException("Construct OSUtils");
     }
 
-    public static Boolean isWindows() {
+    static Boolean isWindows() {
         return System.getProperty("os.name").startsWith("Windows");
     }
 }
diff --git a/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/ProcessUtils.java b/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/ProcessUtils.java
index 11fc869761..500c2724cc 100644
--- a/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/ProcessUtils.java
+++ b/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/ProcessUtils.java
@@ -30,21 +30,23 @@ public class ProcessUtils {
 
     private static final Logger logger = LoggerFactory.getLogger(ProcessUtils.class);
 
+    private ProcessUtils() {
+        throw new IllegalStateException("Utility class");
+    }
+
     /**
      * executeScript
      *
      * @param cmd cmd params
      * @return exit code
      */
-    public static Integer executeScript(String... cmd) {
+    static Integer executeScript(String... cmd) {
 
         int exitCode = -1;
 
         ProcessBuilder processBuilder = new ProcessBuilder(cmd);
         try {
             Process process = processBuilder.start();
-            InputStream in = process.getErrorStream();
-
             StreamGobbler inputStreamGobbler = new StreamGobbler(process.getInputStream());
             StreamGobbler errorStreamGobbler = new StreamGobbler(process.getErrorStream());
 
diff --git a/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/ScriptSender.java b/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/ScriptSender.java
index f7a89d8859..377c318b8e 100644
--- a/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/ScriptSender.java
+++ b/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/ScriptSender.java
@@ -37,13 +37,13 @@ public class ScriptSender {
 
     private String userParams;
 
-    public ScriptSender(Map<String, String> config) {
+    ScriptSender(Map<String, String> config) {
         scriptPath = config.get(ScriptParamsConstants.NAME_SCRIPT_PATH);
         scriptType = Integer.parseInt(config.get(ScriptParamsConstants.NAME_SCRIPT_TYPE));
         userParams = config.get(ScriptParamsConstants.NAME_SCRIPT_USER_PARAMS);
     }
 
-    public AlertResult sendScriptAlert(String msg) {
+    AlertResult sendScriptAlert(String msg) {
         AlertResult alertResult = new AlertResult();
         if (ScriptType.of(scriptType).equals(ScriptType.SHELL)) {
             return executeShellScript(msg);
@@ -54,7 +54,7 @@ public class ScriptSender {
     private AlertResult executeShellScript(String msg) {
         AlertResult alertResult = new AlertResult();
         alertResult.setStatus("false");
-        if (OSUtils.isWindows()) {
+        if (Boolean.TRUE.equals(OSUtils.isWindows())) {
             alertResult.setMessage("shell script not support windows os");
             return alertResult;
         }
diff --git a/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/StreamGobbler.java b/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/StreamGobbler.java
index cde0c7914d..2ec25280b4 100644
--- a/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/StreamGobbler.java
+++ b/dolphinscheduler-alert-plugin/dolphinscheduler-alert-script/src/main/java/org/apache/dolphinscheduler/plugin/alert/script/StreamGobbler.java
@@ -32,7 +32,7 @@ public class StreamGobbler extends Thread {
 
     private static final Logger logger = LoggerFactory.getLogger(StreamGobbler.class);
 
-    InputStream inputStream;
+    private InputStream inputStream;
 
     StreamGobbler(InputStream inputStream) {
         this.inputStream = inputStream;