Method put

vm/JavaAPI/src/java/util/Hashtable.java:693–724

Associate the specified value with the specified key in this Hashtable. If the key already exists, the old value is replaced. The key and value cannot be null. @param key the key to add. @param value the value to add. @return the old value associated with the specified

(K key, V value)

     * @see java.lang.Object#equals
     */
    @Override
    public synchronized V put(K key, V value) {
        if (key != null && value != null) {
            int hash = key.hashCode();
            int index = (hash & 0x7FFFFFFF) % elementData.length;
            Entry<K, V> entry = elementData[index];
            while (entry != null && !entry.equalsKey(key, hash)) {
                entry = entry.next;
            }
            if (entry == null) {
                modCount++;
                if (++elementCount > threshold) {
                    rehash();
                    index = (hash & 0x7FFFFFFF) % elementData.length;
                }
                if (index < firstSlot) {
                    firstSlot = index;
                }
                if (index > lastSlot) {
                    lastSlot = index;
                }
                entry = newEntry(key, value, hash);
                entry.next = elementData[index];
                elementData[index] = entry;
                return null;
            }
            V result = entry.value;
            entry.value = value;
            return result;
        }
        throw new NullPointerException();
    }

    /**
     * Copies every mapping to this {@code Hashtable} from the specified map.