“Almost every ruler who has destroyed freedom sought at first to keep its outward form. This has been evident from Augustus down to the present day. Thus, these rulers flattered themselves that they would be able to add to the moral authority, which always stems from public consent, those advantages which absolute power can alone bestow. They have almost all failed in this endeavour and have soon realized that it was impossible to maintain for long those false appearances unsupported by reality.”

#勇哥带你学Java#
Set接口与接口实现类
无序、不可重复

HashSet
哈希表边存放的是哈希值。
HashSet这个类实现了Set集合，实际为一个HashMap的实例。
HashSet 存储元素的顺序并不是按照存入时的顺序。而是按照哈希值来存的所以取数据也是按照哈希值取得。元素的哈希值是通过元素的hashcode 方法来获取的, HashSet 首先判断两个元素的哈希值，如果哈希值一样（哈希冲突，也叫哈希碰撞），接着会比较equals 方法 如果 equls 结果为 true，HashSet 就视为同一个元素。如果 equals 为 false 就不是同一个元素。HashSet 通过 hashCode 值来确定元素在内存中的位置。 一个 hashCode 位置上可以存放多个元素。

LinkedHashSet
能保证怎么存就怎么取的set集合对象。
LinkedHashSet是一个哈希表和链表的结合，且是一个双向链表。
LinkedHashSet 底层使用 LinkedHashMap 来保存所有元素。
继承与 HashSet，其所有的方法操作上又与 HashSet 相同

#情感语录#

非让现实给你一巴掌，你才知道社会有多虚伪；非让所谓的朋友把你伤的什么都不是，你才知道人心可畏。

Don't let reality slap you, you just know how false the society is; Until the so-called friends hurt you nothing, you will know that people are awesome.

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