小结：POI写Excel公式（函数）及从Excel中读取公式计算值

//写公式：

HSSFCEll newCell = row.createCell(newColIndex);

newCell.setCellFormula("A1+B1");

newCell.setCellType(Cell.CELL_TYPE_FORMULA);

读公式值：

HSSFFormuulaEvaluator eva = new HSSFFormuulaEvaluator(workbook);

double result = eva.evaluete(newCell).getNumberValue();

将1、2、3...列号转换为Excel列号（A/B/C...）

public static String toRadix(Integer num){
String[] array = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
int count = 26;
String out = "";
if(num/count != 0){
out = array[num/count - 1];
if(num%count == 0){
out = out + array[num%count];
}else{
out = out + array[num%count - 1];
}
}else{
out = array[num -1 ];
}
return out;

}