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/* ====================================================================
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The ASF licenses this file to You under the Apache License, Version 2.0
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package org.apache.poi.ss.formula;
/**
* Used to help optimise cell evaluation result caching by allowing applications to specify which
* parts of a workbook are final.
* The term final is introduced here to denote immutability or 'having constant definition'.
* This classification refers to potential actions (on the evaluated workbook) by the evaluating
* application. It does not refer to operations performed by the evaluator ({@link
* WorkbookEvaluator}).
*
* General guidelines:
*
* - a plain value cell can be marked as 'final' if it will not be changed after the first call
* to {@link WorkbookEvaluator#evaluate(EvaluationCell)}.
*
* - a formula cell can be marked as 'final' if its formula will not be changed after the first
* call to {@link WorkbookEvaluator#evaluate(EvaluationCell)}. This remains true even if changes
* in dependent values may cause the evaluated value to change.
* - plain value cells should be marked as 'not final' if their plain value value may change.
*
* - formula cells should be marked as 'not final' if their formula definition may change.
* - cells which may switch between plain value and formula should also be marked as 'not final'.
*
*
* Notes:
*
* - If none of the spreadsheet cells is expected to have its definition changed after evaluation
* begins, every cell can be marked as 'final'. This is the most efficient / least resource
* intensive option.
* - To retain freedom to change any cell definition at any time, an application may classify all
* cells as 'not final'. This freedom comes at the expense of greater memory consumption.
* - For the purpose of these classifications, setting the cached formula result of a cell (for
* example in {@link org.apache.poi.ss.usermodel.FormulaEvaluator#evaluateFormulaCell(org.apache.poi.ss.usermodel.Cell)})
* does not constitute changing the definition of the cell.
* - Updating cells which have been classified as 'final' will cause the evaluator to behave
* unpredictably (typically ignoring the update).
*
*/
public interface IStabilityClassifier {
/**
* Convenience implementation for situations where all cell definitions remain fixed after
* evaluation begins.
*/
IStabilityClassifier TOTALLY_IMMUTABLE = new IStabilityClassifier() {
public boolean isCellFinal(int sheetIndex, int rowIndex, int columnIndex) {
return true;
}
};
/**
* Checks if a cell's value(/formula) is fixed - in other words - not expected to be modified
* between calls to the evaluator. (Note - this is an independent concept from whether a
* formula cell's evaluated value may change during successive calls to the evaluator).
*
* @param sheetIndex zero based index into workbook sheet list
* @param rowIndex zero based row index of cell
* @param columnIndex zero based column index of cell
* @return false if the evaluating application may need to modify the specified
* cell between calls to the evaluator.
*/
boolean isCellFinal(int sheetIndex, int rowIndex, int columnIndex);
}