code: public static <K, V> String join(Map<K, V> map, String separator, String keyValueSeparator, boolean isIgnoreNull) {
  		final StringBuilder strBuilder = StrUtil.builder();
  		boolean isFirst = true;
  		for (Entry<K, V> entry : map.entrySet()) {
  			if (false == isIgnoreNull || entry.getKey() != null && entry.getValue() != null) {
  				if (isFirst) {
  					isFirst = false;
  				} else {
  					strBuilder.append(separator);
  				}
  				strBuilder.append(Convert.toStr(entry.getKey())).append(keyValueSeparator).append(Convert.toStr(entry.getValue()));
  			}
  		}
  		return strBuilder.toString();
  	}
docs: 将map转成字符串
  
  @param <K> 键类型
  @param <V> 值类型
  @param map Map
  @param separator entry之间的连接符
  @param keyValueSeparator kv之间的连接符
  @param isIgnoreNull 是否忽略null的键和值
  @return 连接后的字符串
  @since 3.1.1