Collection Set&HashSet&TreeSet(HashMap實現,去重特性)
阿新 • • 發佈:2018-05-17
ima alt for spec trees boolean cti image 分享圖片
一、HashSet
1. 慮重功能特性(HashMap實現)
2. put(key) 如果重復返回false
/** * Adds the specified element to this set if it is not already present. * More formally, adds the specified element <tt>e</tt> to this set if * this set contains no element <tt>e2</tt> such that * <tt>(e==null ? e2==null : e.equals(e2))</tt>. * If this set already contains the element, the call leaves the set * unchanged and returns <tt>false</tt>. * *@param e element to be added to this set * @return <tt>true</tt> if this set did not already contain the specified * element */ public boolean add(E e) { return map.put(e, PRESENT)==null; // 重復返回false }
Collection Set&HashSet&TreeSet(HashMap實現,去重特性)