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+/*
+ * 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.analysis.solvers;
+
+
+/**
+ * Implements the <em>Illinois</em> method for root-finding (approximating
+ * a zero of a univariate real function). It is a modified
+ * {@link RegulaFalsiSolver <em>Regula Falsi</em>} method.
+ *
+ * <p>Like the <em>Regula Falsi</em> method, convergence is guaranteed by
+ * maintaining a bracketed solution. The <em>Illinois</em> method however,
+ * should converge much faster than the original <em>Regula Falsi</em>
+ * method. Furthermore, this implementation of the <em>Illinois</em> method
+ * should not suffer from the same implementation issues as the <em>Regula
+ * Falsi</em> method, which may fail to convergence in certain cases.</p>
+ *
+ * <p>The <em>Illinois</em> method assumes that the function is continuous,
+ * but not necessarily smooth.</p>
+ *
+ * <p>Implementation based on the following article: M. Dowell and P. Jarratt,
+ * <em>A modified regula falsi method for computing the root of an
+ * equation</em>, BIT Numerical Mathematics, volume 11, number 2,
+ * pages 168-174, Springer, 1971.</p>
+ *
+ * @since 3.0
+ */
+public class IllinoisSolver extends BaseSecantSolver {
+
+    /** Construct a solver with default accuracy (1e-6). */
+    public IllinoisSolver() {
+        super(DEFAULT_ABSOLUTE_ACCURACY, Method.ILLINOIS);
+    }
+
+    /**
+     * Construct a solver.
+     *
+     * @param absoluteAccuracy Absolute accuracy.
+     */
+    public IllinoisSolver(final double absoluteAccuracy) {
+        super(absoluteAccuracy, Method.ILLINOIS);
+    }
+
+    /**
+     * Construct a solver.
+     *
+     * @param relativeAccuracy Relative accuracy.
+     * @param absoluteAccuracy Absolute accuracy.
+     */
+    public IllinoisSolver(final double relativeAccuracy,
+                          final double absoluteAccuracy) {
+        super(relativeAccuracy, absoluteAccuracy, Method.ILLINOIS);
+    }
+
+    /**
+     * Construct a solver.
+     *
+     * @param relativeAccuracy Relative accuracy.
+     * @param absoluteAccuracy Absolute accuracy.
+     * @param functionValueAccuracy Maximum function value error.
+     */
+    public IllinoisSolver(final double relativeAccuracy,
+                          final double absoluteAccuracy,
+                          final double functionValueAccuracy) {
+        super(relativeAccuracy, absoluteAccuracy, functionValueAccuracy, Method.PEGASUS);
+    }
+}