MATH-1144

New interface for allowing caller to validate (i.e. modify) the
set of parameters generated by the optimizer.

src/main/java/org/apache/commons/math3/fitting/leastsquares/ParameterValidator.java

@@ -0,0 +1,34 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.math3.fitting.leastsquares;
+
+import org.apache.commons.math3.linear.RealVector;
+
+/**
+ * Interface for validating a set of model parameters.
+ *
+ * @since 3.4
+ */
+public interface ParameterValidator {
+    /**
+     * Validates the set of parameters.
+     *
+     * @param params Input parameters.
+     * @return the validated values.
+     */
+    RealVector validate(RealVector params);
+}