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diff --git a/src/main/java/org/apache/commons/math3/util/Pair.java b/src/main/java/org/apache/commons/math3/util/Pair.java
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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.util;
+
+/**
+ * Generic pair. <br>
+ * Although the instances of this class are immutable, it is impossible to ensure that the
+ * references passed to the constructor will not be modified by the caller.
+ *
+ * @param <K> Key type.
+ * @param <V> Value type.
+ * @since 3.0
+ */
+public class Pair<K, V> {
+    /** Key. */
+    private final K key;
+
+    /** Value. */
+    private final V value;
+
+    /**
+     * Create an entry representing a mapping from the specified key to the specified value.
+     *
+     * @param k Key (first element of the pair).
+     * @param v Value (second element of the pair).
+     */
+    public Pair(K k, V v) {
+        key = k;
+        value = v;
+    }
+
+    /**
+     * Create an entry representing the same mapping as the specified entry.
+     *
+     * @param entry Entry to copy.
+     */
+    public Pair(Pair<? extends K, ? extends V> entry) {
+        this(entry.getKey(), entry.getValue());
+    }
+
+    /**
+     * Get the key.
+     *
+     * @return the key (first element of the pair).
+     */
+    public K getKey() {
+        return key;
+    }
+
+    /**
+     * Get the value.
+     *
+     * @return the value (second element of the pair).
+     */
+    public V getValue() {
+        return value;
+    }
+
+    /**
+     * Get the first element of the pair.
+     *
+     * @return the first element of the pair.
+     * @since 3.1
+     */
+    public K getFirst() {
+        return key;
+    }
+
+    /**
+     * Get the second element of the pair.
+     *
+     * @return the second element of the pair.
+     * @since 3.1
+     */
+    public V getSecond() {
+        return value;
+    }
+
+    /**
+     * Compare the specified object with this entry for equality.
+     *
+     * @param o Object.
+     * @return {@code true} if the given object is also a map entry and the two entries represent
+     *     the same mapping.
+     */
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (!(o instanceof Pair)) {
+            return false;
+        } else {
+            Pair<?, ?> oP = (Pair<?, ?>) o;
+            return (key == null ? oP.key == null : key.equals(oP.key))
+                    && (value == null ? oP.value == null : value.equals(oP.value));
+        }
+    }
+
+    /**
+     * Compute a hash code.
+     *
+     * @return the hash code value.
+     */
+    @Override
+    public int hashCode() {
+        int result = key == null ? 0 : key.hashCode();
+
+        final int h = value == null ? 0 : value.hashCode();
+        result = 37 * result + h ^ (h >>> 16);
+
+        return result;
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public String toString() {
+        return "[" + getKey() + ", " + getValue() + "]";
+    }
+
+    /**
+     * Convenience factory method that calls the {@link #Pair(Object, Object) constructor}.
+     *
+     * @param <K> the key type
+     * @param <V> the value type
+     * @param k First element of the pair.
+     * @param v Second element of the pair.
+     * @return a new {@code Pair} containing {@code k} and {@code v}.
+     * @since 3.3
+     */
+    public static <K, V> Pair<K, V> create(K k, V v) {
+        return new Pair<K, V>(k, v);
+    }
+}