...
@Override
public boolean equals(Object obj) {
    //类型检查
    //...
    return this.name.equals(((People) obj).name) && this.age == ((People) obj).age;
}

//@Override
//public int hashCode() {
//    return name.hashCode() * 37 + age;
//}

public static void main(String[] args) {
    People p1 = new People("foolchild", 24);
    System.out.println(p1.hashCode());

    Map<People, Integer> hashMap = new HashMap<People, Integer>();
    hashMap.put(p1, 1);

    System.out.println(hashMap.get(new People("foolchild", 24)));
} 
...

public V put(K key, V value) {
    if (table == EMPTY_TABLE) {
        inflateTable(threshold);
    }
    if (key == null)
        return putForNullKey(value);
    // 对put进来的key做hash
    int hash = hash(key);
    // 根据hash值确定在table中的index位置
    int i = indexFor(hash, table.length);
    for (Entry<K,V> e = table[i]; e != null; e = e.next) {
        Object k;
        // e.hash值等于hash并且e.key与key逻辑相等或就是同一个引用,满足的话,就是同一个key,value替换为新值
        if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
            V oldValue = e.value;
            e.value = value;
            e.recordAccess(this);
            return oldValue;
        }
    }

    modCount++;
    //这里并发条件下可能造成死循环,resize,可能导致entry的next指针反转
    addEntry(hash, key, value, i);
    return null;
}

final int hash(Object k) {
    int h = hashSeed;
    if (0 != h && k instanceof String) {
        return sun.misc.Hashing.stringHash32((String) k);
    }

    h ^= k.hashCode();

    // This function ensures that hashCodes that differ only by
    // constant multiples at each bit position have a bounded
    // number of collisions (approximately 8 at default load factor).
    h ^= (h >>> 20) ^ (h >>> 12);
    return h ^ (h >>> 7) ^ (h >>> 4);
}

static int indexFor(int h, int length) {
    // assert Integer.bitCount(length) == 1 : "length must be a non-zero power of 2";
    // 对于table.length,为2^n(n > 0)(这个必须的)
    // h & (length - 1) 其实就是 h % length,不过前者效率高的多,这样可以保证分配平均
    return h & (length-1);
}

public V get(Object key) {
    if (key == null)
        return getForNullKey();
    //这里我们讨论的是非空的key,直接看getEntry    
    Entry<K,V> entry = getEntry(key);

    return null == entry ? null : entry.getValue();
}

final Entry<K,V> getEntry(Object key) {
    if (size == 0) {
        return null;
    }
    
    //hash(key) 是否熟悉,忘了的话看上边
    int hash = (key == null) ? 0 : hash(key);
    for (Entry<K,V> e = table[indexFor(hash, table.length)];
         e != null;
         e = e.next) {
        Object k;
        // 这段逻辑是否熟悉,忘了的话看上边,再贴一遍吧
        // e.hash值等于上hash并且e.key与key逻辑相等或就是同一个引用,满足的话,就是同一个entry,返回改entry
        if (e.hash == hash &&
            ((k = e.key) == key || (key != null && key.equals(k))))
            return e;
    }
    return null;
}