我有一个创建线程的代码。我需要知道如何在发射前等待它完成。

Map<String, String> accountsToRaidWith = Functions.getAccountsByCrew(accounts, crew);

            for (Map.Entry<String, String> entry : accountsToRaidWith.entrySet()) {
                BossRaiding R1 = new BossRaiding(entry.getKey(), entry.getValue(), raidid);
                R1.start();
            }

            boolean launched = Functions.launchRaid(raidid, id);

class BossRaiding implements Runnable {
    private Thread t;
    String name;
    String id;
    String raidid;

    BossRaiding (String name, String id, String raidid) {
        this.name = name;
        this.id = id;
        this.raidid = raidid;
    }

    public void run() {
        Functions.joinRaid(raidid, id);
    }

    public void start () {
        if (t == null) {
            t = new Thread (this);
            t.start ();
        }
    }
}

我正在尝试等待所有帐户加入，然后再启动。我似乎找不到一个正确的方法。