DRILL-7780: Fix string reference comparisons
diff --git a/common/src/main/java/org/apache/drill/common/KerberosUtil.java b/common/src/main/java/org/apache/drill/common/KerberosUtil.java
index 368e493..0dfce33 100644
--- a/common/src/main/java/org/apache/drill/common/KerberosUtil.java
+++ b/common/src/main/java/org/apache/drill/common/KerberosUtil.java
@@ -47,7 +47,7 @@
     checkNotNull(realm);
 
     return primary +
-        ((instance != "") ? "/" + instance : "")
+        ((!"".equals(instance)) ? "/" + instance : "")
         + "@" + realm;
   }
 
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/server/BootStrapContext.java b/exec/java-exec/src/main/java/org/apache/drill/exec/server/BootStrapContext.java
index 74a5d96..b090857 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/server/BootStrapContext.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/server/BootStrapContext.java
@@ -139,7 +139,7 @@
               ExecConstants.SERVICE_PRINCIPAL));
         }
 
-        parts[1] = (parts[1] == "") ? "" : KerberosUtil.canonicalizeInstanceName(parts[1], hostName);
+        parts[1] = ("".equals(parts[1])) ? "" : KerberosUtil.canonicalizeInstanceName(parts[1], hostName);
 
         final String canonicalizedPrincipal = KerberosUtil.getPrincipalFromParts(parts[0], parts[1], parts[2]);
         final String keytab = config.getString(ExecConstants.SERVICE_KEYTAB_LOCATION);