lookup.java

来自「EXCEL read and write」· Java 代码 · 共 84 行

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package org.apache.poi.hssf.record.formula.functions;

import org.apache.poi.hssf.record.formula.eval.AreaEval;
import org.apache.poi.hssf.record.formula.eval.ErrorEval;
import org.apache.poi.hssf.record.formula.eval.Eval;
import org.apache.poi.hssf.record.formula.eval.EvaluationException;
import org.apache.poi.hssf.record.formula.eval.OperandResolver;
import org.apache.poi.hssf.record.formula.eval.ValueEval;
import org.apache.poi.hssf.record.formula.functions.LookupUtils.ValueVector;

/**
 * Implementation of Excel function LOOKUP.<p/>
 * 
 * LOOKUP finds an index  row in a lookup table by the first column value and returns the value from another column.
 * 
 * <b>Syntax</b>:<br/>
 * <b>VLOOKUP</b>(<b>lookup_value</b>, <b>lookup_vector</b>, result_vector)<p/>
 * 
 * <b>lookup_value</b>  The value to be found in the lookup vector.<br/>
 * <b>lookup_vector</> An area reference for the lookup data. <br/>
 * <b>result_vector</b> Single row or single column area reference from which the result value is chosen.<br/>
 * 
 * @author Josh Micich
 */
public final class Lookup implements Function {

	public Eval evaluate(Eval[] args, int srcCellRow, short srcCellCol) {
		switch(args.length) {
			case 3:
				break;
			case 2:
				// complex rules to choose lookupVector and resultVector from the single area ref
				throw new RuntimeException("Two arg version of LOOKUP not supported yet");
			default:
				return ErrorEval.VALUE_INVALID;
		}
		
		
		try {
			ValueEval lookupValue = OperandResolver.getSingleValue(args[0], srcCellRow, srcCellCol);
			AreaEval aeLookupVector = LookupUtils.resolveTableArrayArg(args[1]);
			AreaEval aeResultVector = LookupUtils.resolveTableArrayArg(args[2]);
			
			ValueVector lookupVector = createVector(aeLookupVector);
			ValueVector resultVector = createVector(aeResultVector);
			if(lookupVector.getSize() > resultVector.getSize()) {
				// Excel seems to handle this by accessing past the end of the result vector.
				throw new RuntimeException("Lookup vector and result vector of differing sizes not supported yet");
			}
			int index = LookupUtils.lookupIndexOfValue(lookupValue, lookupVector, true);
			
			return resultVector.getItem(index);
		} catch (EvaluationException e) {
			return e.getErrorEval();
		}
	}

	private static ValueVector createVector(AreaEval ae) {
		ValueVector result = LookupUtils.createVector(ae);
		if (result != null) {
			return result;
		}
		// extra complexity required to emulate the way LOOKUP can handles these abnormal cases.
		throw new RuntimeException("non-vector lookup or result areas not supported yet");
	}
}