1 /***
2 * AvgOperator.java
3 *
4 * $Author: mballesteros $
5 * $Date: 2003/11/28 19:18:03 $
6 * $Revision: 1.1 $
7 */
8 package net.sf.jec.namedop;
9
10 import java.util.Collection;
11 import java.util.Iterator;
12 import java.util.Map;
13
14 import net.sf.jec.ConversionException;
15 import net.sf.jec.EvaluationException;
16 import net.sf.jec.ObjectConverter;
17
18
19 /*** AvgOperator acts over a collection of elements, applying its argument operator
20 * to each element, and averaging the results into a total average.
21 *
22 * @author mballesteros
23 */
24 public class AvgOperator extends GroupOperator {
25
26 private boolean throwExceptions;
27
28 /*** Creates a new SumOperator
29 */
30 public AvgOperator() { }
31
32 /*** Returns a function representation String for this operator
33 */
34 public String toFunctionString() {
35 return "Avg(" + argOps[0]
36 + (nestedOp == null? "" : ", "+nestedOp) + ")";
37 }
38
39 /*** Returns an expression String representation for this operator
40 */
41 public String toExpressionString() {
42 return (nestedOp == null? "" : nestedOp.toString()) + ".avg(" + argOps[0] + ")";
43 }
44
45
46 /*** Returns the associated value to the given context and root context
47 * @param rootCtx The root context, needed for operators that require
48 * expression evaluation from root point. Example: Indexer operators
49 * @param ctx The current context where the operator will work over
50 */
51 protected Object directMap(Object rootCtx, Object ctx) throws EvaluationException {
52 try {
53 if (ctx instanceof Collection) {
54 double acc = 0;
55 Iterator it = ((Collection)ctx).iterator();
56 while (it.hasNext()) {
57 acc += ObjectConverter.toDouble(argOps[0].apply(rootCtx, it.next()));
58 }
59 return new Double(acc / ((Collection)ctx).size() );
60 } else if (ctx instanceof Map) {
61 return applyToGroup(rootCtx, (Map)ctx );
62 } else {
63 return null;
64 }
65 } catch (ConversionException ce) {
66 if (throwExceptions) throw new EvaluationException("Error converting value: "+ce.getMessage());
67 else return null;
68 }
69 }
70 }
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