code: public void enter(Symbol sym) {
              Assert.check(shared == 0);
              if (nelems * 3 >= hashMask * 2)
                  dble();
              int hash = getIndex(sym.name);
              Entry old = table[hash];
              if (old == null) {
                  old = sentinel;
                  nelems++;
              }
              Entry e = new Entry(sym, old, elems, this);
              table[hash] = e;
              elems = e;
  
              //notify listeners
              listeners.symbolAdded(sym, this);
          }
docs: Enter symbol sym in this scope.