01: /**
02: * ===========================================
03: * JFreeReport : a free Java reporting library
04: * ===========================================
05: *
06: * Project Info: http://reporting.pentaho.org/
07: *
08: * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
09: *
10: * This library is free software; you can redistribute it and/or modify it under the terms
11: * of the GNU Lesser General Public License as published by the Free Software Foundation;
12: * either version 2.1 of the License, or (at your option) any later version.
13: *
14: * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
15: * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
16: * See the GNU Lesser General Public License for more details.
17: *
18: * You should have received a copy of the GNU Lesser General Public License along with this
19: * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
20: * Boston, MA 02111-1307, USA.
21: *
22: * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
23: * in the United States and other countries.]
24: *
25: * ------------
26: * ColumnDifferenceExpression.java
27: * ------------
28: * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
29: */package org.jfree.report.function;
30:
31: import java.math.BigDecimal;
32:
33: /**
34: * Computes the difference between the given column values. This is almost the same as the formula
35: * <code>[field1] - [field2] - field[3] - .. - [fieldn]</code>. Values that are non-numeric or null
36: * are ignored.
37: *
38: * @author Thomas Morgner
39: */
40: public class ColumnDifferenceExpression extends
41: ColumnAggregationExpression {
42: /**
43: * Default Constructor.
44: */
45: public ColumnDifferenceExpression() {
46: }
47:
48: /**
49: * Return the current expression value.
50: *
51: * @return the value of the function.
52: */
53: public Object getValue() {
54: final Object[] values = getFieldValues();
55: BigDecimal computedResult = null;
56: for (int i = 0; i < values.length; i++) {
57: final Object value = values[i];
58: if (value instanceof Number == false) {
59: continue;
60: }
61:
62: final Number n = (Number) value;
63: final BigDecimal nval = new BigDecimal(n.toString());
64: if (computedResult == null) {
65: computedResult = nval;
66: } else {
67: computedResult = computedResult.subtract(nval);
68: }
69: }
70:
71: return computedResult;
72: }
73: }
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