[doc][jvm] Explanation for isMaximizeEvaluation. (#11691)

Author: kunaljani1100

jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/XGBoost.java

@@ -386,6 +386,16 @@ private static String getMetricNameFromlog(String evalInfo, String[] evalNames)
   }
 
   // visiable for testing
+
+  /**
+   * Decides whether the evaluation metrics are to be maximized or not.
+   *
+   * @param evalInfo The evaluation log string from which the metric name is inferred.
+   * @param evalNames The names of the evaluation matrices.
+   * @param params The parameters that contain information regarding whether the
+   *  evaluation metrics are to be maximized or not.
+   * @return True if the evaluation metrics are to be maximized, false otherwise.
+   */
   public static boolean isMaximizeEvaluation(String evalInfo,
                                              String[] evalNames,
                                              Map<String, Object> params) {