参考:
http://www.pm25.in/api_doc
其他收费的有:
阿里
https://market.aliyun.com/products/57096001/cmapi011250.html?spm=5176.8216963.738024.5.427484b1ZsZBuR#sku=yuncode525000004
京东
https://wx.jcloud.com/market/datas/26/10406
haoservice
http://www.haoservice.com/docs/13
纠正下: 这不叫java 接口