?  	@sun.misc.Contended 
 	static final class Cell {
        volatile long value;
        Cell(long x) { value = x; }
        final boolean cas(long cmp, long val) {
            return UNSAFE.compareAndSwapLong(this, valueOffset, cmp, val);
        }
        // Unsafe mechanics
        private static final sun.misc.Unsafe UNSAFE;
        private static final long valueOffset;
        static {
            try {
                UNSAFE = sun.misc.Unsafe.getUnsafe();
                Class<?> ak = Cell.class;
                valueOffset = UNSAFE.objectFieldOffset
                    (ak.getDeclaredField("value"));
            } catch (Exception e) {
                throw new Error(e);
            }
        }
    }

  	public void add(long x) {
        Cell[] as; long b, v; int m; Cell a;
        if ((as = cells) != null || !casBase(b = base, b + x)) {//(1)
            boolean uncontended = true;
            if (as == null || (m = as.length - 1) < 0 || //(2)
                (a = as[getProbe() & m]) == null ||//(3)
                !(uncontended = a.cas(v = a.value, v + x)))//(4)
                longAccumulate(x, null, uncontended);//(5)
        }
    }
	final boolean casBase(long cmp, long val) {
        return UNSAFE.compareAndSwapLong(this, BASE, cmp, val);
    }

	final void longAccumulate(long x, LongBinaryOperator fn,
                              boolean wasUncontended) {
        int h;//(6)
        if ((h = getProbe()) == 0) {
            ThreadLocalRandom.current(); // force initialization
            h = getProbe();
            wasUncontended = true;
        }
        boolean collide = false;                // True if last slot nonempty
        for (;;) {
            Cell[] as; Cell a; int n; long v;
            if ((as = cells) != null && (n = as.length) > 0) {//(7)
                if ((a = as[(n - 1) & h]) == null) {//(8)
                    if (cellsBusy == 0) {       // Try to attach new Cell
                        Cell r = new Cell(x);   // Optimistically create
                        if (cellsBusy == 0 && casCellsBusy()) {
                            boolean created = false;
                            try {               // Recheck under lock
                                Cell[] rs; int m, j;
                                if ((rs = cells) != null &&
                                    (m = rs.length) > 0 &&
                                    rs[j = (m - 1) & h] == null) {
                                    rs[j] = r;
                                    created = true;
                                }
                            } finally {
                                cellsBusy = 0;
                            }
                            if (created)
                                break;
                            continue;           // Slot is now non-empty
                        }
                    }
                    collide = false;
                }
                else if (!wasUncontended)       // CAS already known to fail
                    wasUncontended = true;      // Continue after rehash
				//(9)               
                else if (a.cas(v = a.value, ((fn == null) ? v + x :
                                             fn.applyAsLong(v, x))))
                    break;
                //(10)
                else if (n >= NCPU || cells != as)
                    collide = false;            // At max size or stale
                //(11)
                else if (!collide)
                    collide = true;
                //(12)
                else if (cellsBusy == 0 && casCellsBusy()) {
                    try {
                        if (cells == as) {      // Expand table unless stale
                            //(12.1)
                            Cell[] rs = new Cell[n << 1];
                            for (int i = 0; i < n; ++i)
                                rs[i] = as[i];
                            cells = rs;
                        }
                    } finally {
                    	//(12.2)
                        cellsBusy = 0;
                    }
                    //(12.3)
                    collide = false;
                    continue;                   // Retry with expanded table
                }
                //(13)為了能找到一個空閑的Cell，重新計算hash值，xorshift算法生成隨機數(shù)。
                h = advanceProbe(h);
            }
            //(14)
            else if (cellsBusy == 0 && cells == as && casCellsBusy()) {
                boolean init = false;
                try {                           // Initialize table
                    if (cells == as) {
                    	//(14.1)
                        Cell[] rs = new Cell[2];
                        //(14.2)
                        rs[h & 1] = new Cell(x);
                        cells = rs;
                        init = true;
                    }
                } finally {
                	//(14.3)
                    cellsBusy = 0;
                }
                if (init)
                    break;
            }
            else if (casBase(v = base, ((fn == null) ? v + x :
                                        fn.applyAsLong(v, x))))
                break;                          // Fall back on using base
        }
    }