PUBDEV-5294 - XGBoost model in Flow doesn't seem to converge (#2055)

* PUBDEV-5294 - XGBoost model in Flow doesn't seem to converge

* Fix issue with DecimalFormat (not thread safe!)

* Fix formatting

h2o-extensions/xgboost/src/main/java/hex/tree/xgboost/XGBoostModel.java

@@ -13,6 +13,9 @@
 import water.fvec.Frame;
 import water.util.Log;
 import hex.ModelMetrics;
+
+import java.text.DecimalFormat;
+import java.text.NumberFormat;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -285,9 +288,28 @@ public static HashMap<String, Object> createParams(XGBoostParameters p, XGBoostO
       Log.info(" " + s.getKey() + " = " + s.getValue());
     }
     Log.info("");
+
+    localizeDecimalParams(params);
     return params;
   }
 
+  /**
+   * Iterates over a set of parameters and applies locale-specific formatting
+   * to decimal ones (Floats and Doubles).
+   *
+   * @param params Parameters to localize
+   */
+  private static void localizeDecimalParams(final HashMap<String, Object> params) {
+    final NumberFormat localizedNumberFormatter = DecimalFormat.getNumberInstance();
+    for (String key : params.keySet()) {
+      final Object value = params.get(key);
+      if (value instanceof Float || value instanceof Double) {
+        final String localizedValue = localizedNumberFormatter.format(value);
+        params.put(key, localizedValue);
+      }
+    }
+  }
+
   @Override
   protected double[] score0(double[] data, double[] preds) {
     return score0(data, preds, 0.0);