    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.math.linear;
    019
    020    import org.apache.commons.math.FieldElement;
    021    import org.apache.commons.math.linear.MatrixVisitorException;
    022
    023    /**
    024     * Default implementation of the {@link FieldMatrixChangingVisitor} interface.
    025     * <p>
    026     * This class is a convenience to create custom visitors without defining all
    027     * methods. This class provides default implementations that do nothing.
    028     * </p>
    029     *
    030     * @param <T> the type of the field elements
    031     * @version $Revision: 1073158 $ $Date: 2011-02-21 22:46:52 +0100 (lun. 21 f??vr. 2011) $
    032     * @since 2.0
    033     */
    034    public class DefaultFieldMatrixChangingVisitor<T extends FieldElement<T>>
    035        implements FieldMatrixChangingVisitor<T> {
    036
    037        /** Zero element of the field. */
    038        private final T zero;
    039
    040        /** Build a new instance.
    041         * @param zero additive identity of the field
    042         */
    043        public DefaultFieldMatrixChangingVisitor(final T zero) {
    044            this.zero = zero;
    045        }
    046
    047        /** {@inheritDoc} */
    048        public void start(int rows, int columns,
    049                          int startRow, int endRow, int startColumn, int endColumn) {
    050        }
    051
    052        /** {@inheritDoc} */
    053        public T visit(int row, int column, T value) throws MatrixVisitorException {
    054            return value;
    055        }
    056
    057        /** {@inheritDoc} */
    058        public T end() {
    059            return zero;
    060        }
    061
    062    }