csv.java

来自「JfreeChart 常用图表例子」· Java 代码 · 共 203 行

/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
 *
 * Project Info:  http://www.jfree.org/jfreechart/index.html
 *
 * This library is free software; you can redistribute it and/or modify it 
 * under the terms of the GNU Lesser General Public License as published by 
 * the Free Software Foundation; either version 2.1 of the License, or 
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License 
 * along with this library; if not, write to the Free Software Foundation, 
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * --------
 * CSV.java
 * --------
 * (C) Copyright 2003, 2004, by Object Refinery Limited.
 *
 * Original Author:  David Gilbert (for Object Refinery Limited);
 * Contributor(s):   -;
 *
 * $Id: CSV.java,v 1.3 2005/02/24 10:44:56 mungady Exp $
 *
 * Changes
 * -------
 * 24-Nov-2003 : Version 1 (DG);
 *
 */

package org.jfree.data.io;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.util.List;

import org.jfree.data.category.CategoryDataset;
import org.jfree.data.category.DefaultCategoryDataset;

/**
 * A utility class for reading {@link CategoryDataset} data from a CSV file.  
 * This initial version is very basic, and won't handle errors in the data 
 * file very gracefully.
 */
public class CSV {

    /** The field delimiter. */
    private char fieldDelimiter;
    
    /** The text delimiter. */
    private char textDelimiter;
     
    /** 
     * Creates a new CSV reader where the field delimiter is a comma, and the 
     * text delimiter is a double-quote.
     */
    public CSV() {
        this(',', '"');    
    }
    
    /**
     * Creates a new reader with the specified field and text delimiters.
     * 
     * @param fieldDelimiter  the field delimiter (usually a comma, semi-colon,
     *                        colon, tab or space).
     * @param textDelimiter  the text delimiter (usually a single or double 
     *                       quote).
     */
    public CSV(char fieldDelimiter, char textDelimiter) {
        this.fieldDelimiter = fieldDelimiter;
        this.textDelimiter = textDelimiter;
    }
    
    /**
     * Reads a {@link CategoryDataset} from a CSV file or input source.
     * 
     * @param in  the input source.
     * 
     * @return A category dataset.
     * 
     * @throws IOException if there is an I/O problem.
     */
    public CategoryDataset readCategoryDataset(Reader in) throws IOException {
        
        DefaultCategoryDataset dataset = new DefaultCategoryDataset();
        BufferedReader reader = new BufferedReader(in);
        List columnKeys = null;
        int lineIndex = 0;
        String line = reader.readLine();
        while (line != null) {
            if (lineIndex == 0) {  // first line contains column keys
                columnKeys = extractColumnKeys(line);
            }
            else {  // remaining lines contain a row key and data values
                extractRowKeyAndData(line, dataset, columnKeys);
            }
            line = reader.readLine();
            lineIndex++;
        }
        return dataset;     
         
    }
    
    /**
     * Extracts the column keys from a string.
     * 
     * @param line  a line from the input file.
     * 
     * @return A list of column keys.
     */
    private List extractColumnKeys(String line) {
        List keys = new java.util.ArrayList();
        int fieldIndex = 0;
        int start = 0;
        for (int i = 0; i < line.length(); i++) {
            if (line.charAt(i) == this.fieldDelimiter) {
                if (fieldIndex > 0) {  // first field is ignored, since 
                                       // column 0 is for row keys
                    String key = line.substring(start, i);
                    keys.add(removeStringDelimiters(key));
                }
                start = i + 1;
                fieldIndex++;
            }
        }
        String key = line.substring(start, line.length());
        keys.add(removeStringDelimiters(key));
        return keys;        
    }
    
    /**
     * Extracts the row key and data for a single line from the input source.
     * 
     * @param line  the line from the input source.
     * @param dataset  the dataset to be populated.
     * @param columnKeys  the column keys.
     */
    private void extractRowKeyAndData(String line,
                                      DefaultCategoryDataset dataset,
                                      List columnKeys) {
        Comparable rowKey = null;
        int fieldIndex = 0;
        int start = 0;
        for (int i = 0; i < line.length(); i++) {
            if (line.charAt(i) == this.fieldDelimiter) {
                if (fieldIndex == 0) {  // first field contains the row key
                    String key = line.substring(start, i);
                    rowKey = removeStringDelimiters(key);
                }
                else {  // remaining fields contain values
                    Double value = Double.valueOf(
                        removeStringDelimiters(line.substring(start, i))
                    );
                    dataset.addValue(
                        value, rowKey, 
                        (Comparable) columnKeys.get(fieldIndex - 1)
                    );
                }
                start = i + 1;
                fieldIndex++;
            }
        }
        Double value = Double.valueOf(
            removeStringDelimiters(line.substring(start, line.length()))
        );
        dataset.addValue(
            value, rowKey, (Comparable) columnKeys.get(fieldIndex - 1)
        ); 
    }
    
    /**
     * Removes the string delimiters from a key (as well as any white space 
     * outside the delimiters).
     * 
     * @param key  the key (including delimiters).
     * 
     * @return The key without delimiters.
     */
    private String removeStringDelimiters(String key) {
        String k = key.trim();
        if (k.charAt(0) == this.textDelimiter) {
            k = k.substring(1);
        }
        if (k.charAt(k.length() - 1) == this.textDelimiter) {
            k = k.substring(0, k.length() - 1);
        }
        return k;
    }
    
}