ParserATNSimulator.java 文件源码

/**
 * 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 previousD 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
 */
@Nullable
protected DFAState getExistingTargetState(@NotNull DFAState previousD, int t) {
    DFAState[] edges = previousD.edges;
    if (edges == null || t + 1 < 0 || t + 1 >= edges.length) {
        return null;
    }

    return edges[t + 1];
}