HashMap不是线程安全的，HashTable是线程安全。HashMap允许空（null）的键和值（key），HashTable则不允许。HashMap性能优于Hashtable。

Map1.Map是一个以键值对存储的接口。Map下有两个具体的实现，分别是HashMap和HashTable.2.HashMap是线程非安全的，HashTable是线程安全的，所以HashMap的效率高于HashTable.3.HashMap允许键或值为空，而HashTable不允许键或值为空.

九大隐式对象

输入/输出对象： request response out作用域通信对象： session application pageContextServlet 对象： page config错误对象： exceptio
https://www.linkedin.com/help/linkedin/answers/丽江外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/桂林外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/保定外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/洛阳外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/义乌外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/三亚外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/台州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/珠海外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/惠州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/嘉兴外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/绍兴外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/金华外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/厦门外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/大连外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/扬州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/徐州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/南通外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/常州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/泉州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/温州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/佛山外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/无锡外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/深圳外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/乌鲁木齐外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/呼和浩特外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/西宁外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/西安外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/贵阳外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/海口外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/长沙外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/郑州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/南昌外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/合肥外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/南京外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/长春外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/太原外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/银川外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/南宁外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/兰州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/昆明外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/成都外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/武汉外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/广州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/济南外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/福州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/杭州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/哈尔滨外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/沈阳外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/石家庄外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/重庆外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/上海外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/天津外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/北京外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/宁波外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/青岛外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/东莞外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/苏州外围【vx：5.2.2.0.5.2.6.4】
https://www.linkedin.com/help/linkedin/answers/丽江外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/桂林外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/保定外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/洛阳外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/义乌外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/三亚外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/台州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/珠海外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/惠州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/嘉兴外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/绍兴外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/金华外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/厦门外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/大连外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/扬州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/徐州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/南通外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/常州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/泉州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/温州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/佛山外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/无锡外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/深圳外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/乌鲁木齐外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/呼和浩特外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/西宁外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/西安外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/贵阳外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/海口外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/长沙外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/郑州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/南昌外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/合肥外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/南京外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/长春外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/太原外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/银川外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/南宁外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/兰州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/昆明外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/成都外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/武汉外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/广州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/济南外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/福州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/杭州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/哈尔滨外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/沈阳外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/石家庄外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/重庆外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/上海外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/天津外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/北京外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/宁波外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/青岛外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/东莞外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/苏州外围【vx：8.1.3.4.3.6.2.8】
https://www.linkedin.com/help/linkedin/answers/丽江外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/桂林外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/保定外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/洛阳外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/义乌外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/三亚外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/台州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/珠海外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/惠州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/嘉兴外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/绍兴外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/金华外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/厦门外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/大连外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/扬州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/徐州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/南通外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/常州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/泉州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/温州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/佛山外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/无锡外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/深圳外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/乌鲁木齐外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/呼和浩特外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/西宁外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/西安外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/贵阳外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/海口外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/长沙外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/郑州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/南昌外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/合肥外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/南京外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/长春外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/太原外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/银川外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/南宁外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/兰州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/昆明外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/成都外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/武汉外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/广州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/济南外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/福州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/杭州外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/哈尔滨外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/沈阳外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/石家庄外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/重庆外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/上海外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/天津外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/北京外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/宁波外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/青岛外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/东莞外围【vx：9.2.3.6.8.1.8】
https://www.linkedin.com/help/linkedin/answers/苏州外围【vx：9.2.3.6.8.1.8】