PR update - clarify duplicated options code

JAVA-5834

Author: rozza

driver-core/src/main/com/mongodb/ConnectionString.java

@@ -1260,20 +1260,25 @@ private void validateProxyParameters(final Map<String, List<String>> optionsMap)
                     "Both proxyUsername and proxyPassword must be set together. They cannot be set individually");
         }
 
-        if (proxyHost != null && optionsMap.get("proxyhost").size() > 1) {
+        if (containsDuplicatedOptions("proxyhost", optionsMap)) {
             throw new IllegalArgumentException("Duplicated values for proxyHost: " + optionsMap.get("proxyhost"));
         }
-        if (proxyPort != null && optionsMap.get("proxyport").size() > 1) {
+        if (containsDuplicatedOptions("proxyport", optionsMap)) {
             throw new IllegalArgumentException("Duplicated values for proxyPort: " + optionsMap.get("proxyport"));
         }
-        if (proxyPassword != null && optionsMap.get("proxypassword").size() > 1) {
+        if (containsDuplicatedOptions("proxypassword", optionsMap)) {
             throw new IllegalArgumentException("Duplicated values for proxyPassword: " + optionsMap.get("proxypassword"));
         }
-        if (proxyUsername != null && optionsMap.get("proxyusername").size() > 1) {
+        if (containsDuplicatedOptions("proxyusername", optionsMap)) {
             throw new IllegalArgumentException("Duplicated values for proxyUsername: " + optionsMap.get("proxyusername"));
         }
     }
 
+    private boolean containsDuplicatedOptions(final String optionName, final Map<String, List<String>> optionsMap) {
+        List<String> optionList = optionsMap.get(optionName);
+        return optionList != null && optionList.size() > 1;
+    }
+
     private int countOccurrences(final String haystack, final String needle) {
         return haystack.length() - haystack.replace(needle, "").length();
     }