protected DFAState getExistingTargetState(DFAState s, int t) {
		if (s.edges == null || t < MIN_DFA_EDGE || t > MAX_DFA_EDGE) {
			return null;
		}

		DFAState target = s.edges[t - MIN_DFA_EDGE];
		if (debug && target != null) {
			System.out.println("reuse state "+s.stateNumber+
							   " edge to "+target.stateNumber);
		}

		return target;
	}
Get an existing target state for an edge in the DFA. If the target state
for the edge has not yet been computed or is otherwise not available,
this method returns {@code null}.

@param s The current DFA state
@param t The next input symbol
@return The existing target DFA state for the given input symbol
{@code t}, or {@code null} if the target state for this edge is not
already cached
runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java