Merge pull request #722 from goldonship/patch-1

Update StringUtil.java

apm-commons/apm-util/src/main/java/org/apache/skywalking/apm/util/StringUtil.java

@@ -21,10 +21,7 @@ package org.apache.skywalking.apm.util;
 
 public final class StringUtil {
     public static boolean isEmpty(String str) {
-        if (str == null || "".equals(str) || str.length() == 0) {
-            return true;
-        }
-        return false;
+        return str == null || str.length() == 0;
     }
 
     public static String join(final char delimiter, final String... strings) {