refactor: use StandardCharsets.UTF_8 instead of string literal

Author: oldratlee

library/src/main/java/com/alibaba/dcm/agent/DcmAgent.java

@@ -10,12 +10,12 @@
 import java.lang.instrument.Instrumentation;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
-import java.nio.charset.StandardCharsets;
 import java.text.SimpleDateFormat;
 import java.util.*;
 import java.util.logging.Logger;
 
 import static java.lang.String.format;
+import static java.nio.charset.StandardCharsets.UTF_8;
 
 /**
  * DCM agent.
@@ -118,7 +118,7 @@ private static PrintWriter getFilePrintWriter(@Nullable List<String> files) thro
         if (null == files) return null;
 
         FileOutputStream fileOutputStream = new FileOutputStream(files.get(0), false);
-        final OutputStreamWriter outputStreamWriter = new OutputStreamWriter(fileOutputStream, StandardCharsets.UTF_8);
+        final OutputStreamWriter outputStreamWriter = new OutputStreamWriter(fileOutputStream, UTF_8);
 
         return new PrintWriter(outputStreamWriter, true);
     }

tool/src/main/java/com/alibaba/dcm/tool/DcmTool.java

@@ -14,6 +14,7 @@
 import java.util.Scanner;
 
 import static java.lang.System.exit;
+import static java.nio.charset.StandardCharsets.UTF_8;
 
 /**
  * DCM Tool.
@@ -108,7 +109,7 @@ private static void doDcmActionViaAgent(@Nonnull String action, @Nonnull String[
     private static boolean printDcmResult(@Nonnull String tmpFile) throws IOException {
         boolean actionSuccess = false;
 
-        final List<String> lines = FileUtils.readLines(new File(tmpFile), "UTF-8");
+        final List<String> lines = FileUtils.readLines(new File(tmpFile), UTF_8);
 
         final int lastIdx = lines.size() - 1;
         final String lastLine = lines.get(lastIdx);