Remove null check

*Move string literal to the left side of comparison
Null check is performed by String.equalsIgnorecase hence removed

Issue-Id: CCSDK-117
Change-Id: I48c8815f9f20a1c6e86c8b4af8966c9945d5b0c7
Signed-off-by: surya-huawei <a.u.surya@huawei.com>
diff --git a/restapi-call-node/provider/src/main/java/org/onap/ccsdk/sli/plugins/restapicall/Format.java b/restapi-call-node/provider/src/main/java/org/onap/ccsdk/sli/plugins/restapicall/Format.java
index 573c85f..776485a 100644
--- a/restapi-call-node/provider/src/main/java/org/onap/ccsdk/sli/plugins/restapicall/Format.java
+++ b/restapi-call-node/provider/src/main/java/org/onap/ccsdk/sli/plugins/restapicall/Format.java
@@ -25,11 +25,9 @@
     JSON, XML;
 
     public static Format fromString(String s) {
-        if (s == null)
-            return null;
-        if (s.equalsIgnoreCase("json"))
+        if ("json".equalsIgnoreCase(s))
             return JSON;
-        if (s.equalsIgnoreCase("xml"))
+        if ("xml".equalsIgnoreCase(s))
             return XML;
         throw new IllegalArgumentException("Invalid value for format: " + s);
     }