HashMap hashMap = new HashMap<>();
java.util.HashMap
public HashMap(),给负载因子赋值为：0.75；
this.loadFactor = DEFAULT_LOAD_FACTOR;
hashMap.put("hello1", "world1");
putVal(int hash, K key, V value, boolean onlyIfAbsent,boolean evict)
java.util.HashMap.resize()
在resize()方法中， Node
【HashMap(jdk8)】底层Node(k,v)[]数组的长度n,与key的哈希值hash与key的哈希值无符号右移16位取与运算；；
n = table.length;
hash = (h = key.hashCode()) ^ (h >>> 16)
location = （n - 1) ^ hash
