DFA.java 文件源码

/**
 * Sets whether this is a precedence DFA. If the specified value differs
 * from the current DFA configuration, the following actions are taken;
 * otherwise no changes are made to the current DFA.
 *
 * <ul>
 * <li>The {@link #states} map is cleared</li>
 * <li>If {@code precedenceDfa} is {@code false}, the initial state
 * {@link #s0} is set to {@code null}; otherwise, it is initialized to a new
 * {@link DFAState} with an empty outgoing {@link DFAState#edges} array to
 * store the start states for individual precedence values.</li>
 * <li>The {@link #precedenceDfa} field is updated</li>
 * </ul>
 *
 * @param precedenceDfa {@code true} if this is a precedence DFA; otherwise,
 * {@code false}
 */
public final synchronized void setPrecedenceDfa(boolean precedenceDfa) {
    if (this.precedenceDfa != precedenceDfa) {
        this.states.clear();
        if (precedenceDfa) {
            DFAState precedenceState = new DFAState(new ATNConfigSet());
            precedenceState.edges = new DFAState[0];
            precedenceState.isAcceptState = false;
            precedenceState.requiresFullContext = false;
            this.s0 = precedenceState;
        }
        else {
            this.s0 = null;
        }

        this.precedenceDfa = precedenceDfa;
    }
}