如何使用图论调度执行顺序？ [重复]

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class Plugin {
    Set<Plugin> dependencies;
    boolean started, starting;

    Plugin(Set<Plugin> deps) { dependencies = deps; }

    void start() {
        if (started) { /* already initialized */ }
        else if (starting) { throw new IllegalArgumentException(\"Cyclic plugin dependency\"); }
        else {
            starting = true;
            for (Plugin p : dependencies) { p.start(); }
            /* initialize this plugin here */
            starting = false;
            started = true;
        }
    }
}