code: public Border setBorderStyle(final BorderStyle borderStyle) {
  
          if (borderStyle == BorderStyle.INITIAL
                  || borderStyle == BorderStyle.INHERIT) {
              throw new InvalidValueException("the given borderStyle cannot be "
                      + borderStyle.getCssValue());
          }
  
          final StringBuilder cssValueBuilder = new StringBuilder();
  
          if (borderWidthValue != null) {
              cssValueBuilder.append(borderWidthValue).append(' ');
          }
  
          if (borderStyle != null) {
              cssValueBuilder.append(borderStyle.getCssValue()).append(' ');
          }
  
          if (borderColorCssValues != null) {
              cssValueBuilder.append(borderColorCssValues.getValue()).append(' ');
          }
  
          final String trimmedCssValue = StringBuilderUtil
                  .getTrimmedString(cssValueBuilder).toString();
          cssValue = trimmedCssValue.isEmpty() ? INHERIT : trimmedCssValue;
  
          this.borderStyle = borderStyle;
  
          if (getStateChangeInformer() != null) {
              getStateChangeInformer().stateChanged(this);
          }
          return this;
      }
docs: to set the border style.
  
  @param borderStyle
  @return the current object.
  @author WFF
  @since 1.0.0