code: public static CellStyle setBorder(CellStyle cellStyle, BorderStyle borderSize, IndexedColors colorIndex) {
  		cellStyle.setBorderBottom(borderSize);
  		cellStyle.setBottomBorderColor(colorIndex.index);
  
  		cellStyle.setBorderLeft(borderSize);
  		cellStyle.setLeftBorderColor(colorIndex.index);
  
  		cellStyle.setBorderRight(borderSize);
  		cellStyle.setRightBorderColor(colorIndex.index);
  
  		cellStyle.setBorderTop(borderSize);
  		cellStyle.setTopBorderColor(colorIndex.index);
  
  		return cellStyle;
  	}
docs: 设置cell的四个边框粗细和颜色
  
  @param cellStyle {@link CellStyle}
  @param borderSize 边框粗细{@link BorderStyle}枚举
  @param colorIndex 颜色的short值
  @return {@link CellStyle}