[Java] Java源码解析ConcurrentHashMap的初始化

private final node<k,v>[] inittable() {
  node<k,v>[] tab; int sc;
  while ((tab = table) == null || tab.length == 0) { // 第一次检查
    if ((sc = sizectl) < 0)
    thread.yield(); // lost initialization race; just spin
    else if (u.compareandswapint(this, sizectl, sc, -1)) {
    try {
      if ((tab = table) == null || tab.length == 0) {// 第二次检查
      int n = (sc > 0) ? sc : default_capacity;
      @suppresswarnings("unchecked")
      node<k,v>[] nt = (node<k,v>[])new node<?,?>[n];
      table = tab = nt;
      sc = n - (n >>> 2);
      }
    } finally {
      sizectl = sc;
    }
    break;
    }
  }
  return tab;
  }