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    
022    /**
023     * Default implementation of the {@link FieldMatrixPreservingVisitor} 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 $Revision: 778191 $ $Date: 2009-05-24 12:44:52 -0400 (Sun, 24 May 2009) $
031     * @since 2.0
032     */
033    public class DefaultFieldMatrixPreservingVisitor<T extends FieldElement<T>>
034        implements FieldMatrixPreservingVisitor<T> {
035    
036        /** Zero element of the field. */
037        private final T zero;
038    
039        /** Build a new instance.
040         * @param zero additive identity of the field
041         */
042        public DefaultFieldMatrixPreservingVisitor(final T zero) {
043            this.zero = zero;
044        }
045    
046        /** {@inheritDoc} */
047        public void start(int rows, int columns,
048                          int startRow, int endRow, int startColumn, int endColumn) {
049        }
050    
051        /** {@inheritDoc} */
052        public void visit(int row, int column, T value)
053            throws MatrixVisitorException {
054        }
055    
056        /** {@inheritDoc} */
057        public T end() {
058            return zero;
059        }
060    
061    }