Refactor: Extract validation logic to shared method

Co-authored-by: maurever <11465784+maurever@users.noreply.github.com>

Author: Copilot

h2o-algos/src/main/java/hex/tree/gbm/GBMModel.java

@@ -315,34 +315,8 @@ public TwoDimTable[][] getFeatureInteractionsTable(int maxInteractionDepth, int
 
   @Override
   public double getFriedmanPopescusH(Frame frame, String[] vars) {
-    // Validate vars parameter
-    if (vars == null || vars.length == 0) {
-      throw new IllegalArgumentException(
-              "Calculating H statistics error: 'vars' parameter cannot be null or empty. " +
-              "Please specify at least one variable.");
-    }
-
-    // Validate that all specified columns exist in the frame and are numeric
-    for (String varName : vars) {
-      if (varName == null) {
-        throw new IllegalArgumentException(
-                "Calculating H statistics error: 'vars' parameter contains a null value.");
-      }
-      Vec col = frame.vec(varName);
-      if (col == null) {
-        throw new IllegalArgumentException(
-                "Calculating H statistics error: column '" + varName + "' does not exist in the frame.");
-      }
-      if (!col.isNumeric()) {
-        throw new IllegalArgumentException(
-                "Calculating H statistics error: column '" + varName + "' is not numeric. " +
-                "H statistics can only be calculated for numeric variables.");
-      }
-      if (col.isBad() || col.isConst()) {
-        throw new IllegalArgumentException(
-                "Calculating H statistics error: column '" + varName + "' contains only missing or constant values.");
-      }
-    }
+    // Validate input parameters
+    validateFriedmanPopescusHInput(frame, vars);
 
     Frame adaptFrm = removeSpecialNNonNumericColumns(frame);
 

h2o-core/src/main/java/hex/FriedmanPopescusHCollector.java

@@ -1,11 +1,50 @@
 package hex;
 
 import water.fvec.Frame;
+import water.fvec.Vec;
 
 /**
  * Implementors of this interface have Friedman & Popescu's H calculation implemented.
  */
 public interface FriedmanPopescusHCollector {
 
     double getFriedmanPopescusH(Frame frame, String[] vars);
+    
+    /**
+     * Validates the input parameters for Friedman Popescu's H statistic calculation.
+     * 
+     * @param frame The input frame
+     * @param vars The variables to calculate H statistic for
+     * @throws IllegalArgumentException if validation fails
+     */
+    default void validateFriedmanPopescusHInput(Frame frame, String[] vars) {
+        // Validate vars parameter
+        if (vars == null || vars.length == 0) {
+            throw new IllegalArgumentException(
+                    "Calculating H statistics error: 'vars' parameter cannot be null or empty. " +
+                    "Please specify at least one variable.");
+        }
+
+        // Validate that all specified columns exist in the frame and are numeric
+        for (String varName : vars) {
+            if (varName == null) {
+                throw new IllegalArgumentException(
+                        "Calculating H statistics error: 'vars' parameter contains a null value.");
+            }
+            Vec col = frame.vec(varName);
+            if (col == null) {
+                throw new IllegalArgumentException(
+                        "Calculating H statistics error: column '" + varName + "' does not exist in the frame.");
+            }
+            if (!col.isNumeric()) {
+                throw new IllegalArgumentException(
+                        "Calculating H statistics error: column '" + varName + "' is not numeric. " +
+                        "H statistics can only be calculated for numeric variables.");
+            }
+            if (col.isBad() || col.isConst()) {
+                throw new IllegalArgumentException(
+                        "Calculating H statistics error: column '" + varName + "' contains only missing or constant values.");
+            }
+        }
+    }
 }

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

@@ -1036,34 +1036,8 @@ protected Frame removeSpecialNNonNumericColumns(Frame frame) {
 
   @Override
   public double getFriedmanPopescusH(Frame frame, String[] vars) {
-    // Validate vars parameter
-    if (vars == null || vars.length == 0) {
-      throw new IllegalArgumentException(
-              "Calculating H statistics error: 'vars' parameter cannot be null or empty. " +
-              "Please specify at least one variable.");
-    }
-
-    // Validate that all specified columns exist in the frame and are numeric
-    for (String varName : vars) {
-      if (varName == null) {
-        throw new IllegalArgumentException(
-                "Calculating H statistics error: 'vars' parameter contains a null value.");
-      }
-      Vec col = frame.vec(varName);
-      if (col == null) {
-        throw new IllegalArgumentException(
-                "Calculating H statistics error: column '" + varName + "' does not exist in the frame.");
-      }
-      if (!col.isNumeric()) {
-        throw new IllegalArgumentException(
-                "Calculating H statistics error: column '" + varName + "' is not numeric. " +
-                "H statistics can only be calculated for numeric variables.");
-      }
-      if (col.isBad() || col.isConst()) {
-        throw new IllegalArgumentException(
-                "Calculating H statistics error: column '" + varName + "' contains only missing or constant values.");
-      }
-    }
+    // Validate input parameters
+    validateFriedmanPopescusHInput(frame, vars);
 
     Frame adaptFrm = removeSpecialNNonNumericColumns(frame);