    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements.  See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache License, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License.  You may obtain a copy of the License at
    008     *
    009     *      http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     * Unless required by applicable law or agreed to in writing, software
    012     * distributed under the License is distributed on an "AS IS" BASIS,
    013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     * See the License for the specific language governing permissions and
    015     * limitations under the License.
    016     */
    017
    018    package org.apache.commons.math3.linear;
    019
    020    import org.apache.commons.math3.FieldElement;
    021
    022    /**
    023     * Default implementation of the {@link FieldMatrixChangingVisitor} interface.
    024     * <p>
    025     * This class is a convenience to create custom visitors without defining all
    026     * methods. This class provides default implementations that do nothing.
    027     * </p>
    028     *
    029     * @param <T> the type of the field elements
    030     * @version $Id: DefaultFieldMatrixChangingVisitor.java 1416643 2012-12-03 19:37:14Z tn $
    031     * @since 2.0
    032     */
    033    public class DefaultFieldMatrixChangingVisitor<T extends FieldElement<T>>
    034        implements FieldMatrixChangingVisitor<T> {
    035        /** Zero element of the field. */
    036        private final T zero;
    037
    038        /** Build a new instance.
    039         * @param zero additive identity of the field
    040         */
    041        public DefaultFieldMatrixChangingVisitor(final T zero) {
    042            this.zero = zero;
    043        }
    044
    045        /** {@inheritDoc} */
    046        public void start(int rows, int columns,
    047                          int startRow, int endRow, int startColumn, int endColumn) {
    048        }
    049
    050        /** {@inheritDoc} */
    051        public T visit(int row, int column, T value) {
    052            return value;
    053        }
    054
    055        /** {@inheritDoc} */
    056        public T end() {
    057            return zero;
    058        }
    059    }