目录
HashSet底层
是一个HashMap,只不过HashMap里面每个key对应的value值都是一样的PRESENT private static final Object PRESENT = new Object();
HashSet构造函数
public HashSet() {
map = new HashMap<>();//new HashSet实际上是new HashMap();
}
HaseSet add分析
// Dummy value to associate with an Object in the backing Map
private static final Object PRESENT = new Object();
public boolean add(E e) {
return map.put(e, PRESENT)==null;//add其实是在HashMap里put一个key,对一个的value是固定的PRESENT
}
TreeSet底层
是一个TreeMap,只不过HashMap里面每个key对应的value值都是一样的PRESENT private static final Object PRESENT = new Object();
TreeSet构造函数
public TreeSet() {
this(new TreeMap<E,Object>());//new TreeSet实际上是new TreeMap()
}
TreeSet add分析
//是向TreeMap里面put一个key,对应value是固定的PRESENT
public boolean add(E e) { return m.put(e, PRESENT)==null; }