@Override
    public boolean remove(Object o) {
        return map.remove(o) == PRESENT;
    }
Removes the specified element from this set if it is present. More
formally, removes an element <tt>e</tt> such that
<tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>, if this
set contains such an element. Returns <tt>true</tt> if this set contained
the element (or equivalently, if this set changed as a result of the
call). (This set will not contain the element once the call returns.)

@param o object to be removed from this set, if present
@return <tt>true</tt> if the set contained the specified element
core/common/src/main/java/com/alipay/sofa/rpc/common/struct/ConcurrentHashSet.java