1.AtomicReference大部分方法带有Object标识

    private volatile V value;

    /**
     * Creates a new AtomicReference with the given initial value.
     *
     * @param initialValue the initial value
     */
    public AtomicReference(V initialValue) {
        value = initialValue;
    }

    /**
     * Creates a new AtomicReference with null initial value.
     */
    public AtomicReference() {
    }

    public final V get() {
        return value;
    }

    public final V getAndSet(V newValue) {
        return (V)unsafe.getAndSetObject(this, valueOffset, newValue);
    }

    public final Object getAndSetObject(Object var1, long var2, Object var4) {
        Object var5;
        do {
            var5 = this.getObjectVolatile(var1, var2);
        } while(!this.compareAndSwapObject(var1, var2, var5, var4));

        return var5;
    }

设置引用调用的是getAndSetObject，范式还是一样CAS+循环。

    public final V getAndUpdate(UnaryOperator<V> updateFunction) {
        V prev, next;
        do {
            prev = get();
            next = updateFunction.apply(prev);
        } while (!compareAndSet(prev, next));
        return prev;
    }

    public final V getAndAccumulate(V x,
                                    BinaryOperator<V> accumulatorFunction) {
        V prev, next;
        do {
            prev = get();
            next = accumulatorFunction.apply(prev, x);
        } while (!compareAndSet(prev, next));
        return prev;
    }

2.抽象类AtomicReferenceFieldUpdater

基于反射，可以对指定类的指定volatile引用字段进行原子更新。此类设计用于原子数据结构，使数据结构中多个引用字段能够独立地进行原子更新，如下所示：

 class Node {
   private volatile Node left, right;

   private static final AtomicReferenceFieldUpdater<Node, Node> leftUpdater =
     AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "left");
   private static AtomicReferenceFieldUpdater<Node, Node> rightUpdater =
     AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "right");

   Node getLeft() { return left; }
   boolean compareAndSetLeft(Node expect, Node update) {
     return leftUpdater.compareAndSet(this, expect, update);
   }
   // ... and so on
 }

构造器：

     * @param tclass the class of the objects holding the field
     * @param vclass the class of the field
     * @param fieldName the name of the field to be updated
     * @param <U> the type of instances of tclass
     * @param <W> the type of instances of vclass

    public static <U,W> AtomicReferenceFieldUpdater<U,W> newUpdater(Class<U> tclass,
                                                                    Class<W> vclass,
                                                                    String fieldName) {
        return new AtomicReferenceFieldUpdaterImpl<U,W>
            (tclass, vclass, fieldName, Reflection.getCallerClass());
    }

AtomicReferenceFieldUpdaterImpl.getAndSet：

        public final V getAndSet(T obj, V newValue) {
            accessCheck(obj);
            valueCheck(newValue);
            return (V)U.getAndSetObject(obj, offset, newValue);
        }

AtomicReferenceFieldUpdater.getAndUpdate

    public final V getAndUpdate(T obj, UnaryOperator<V> updateFunction) {
        V prev, next;
        do {
            prev = get(obj);
            next = updateFunction.apply(prev);
        } while (!compareAndSet(obj, prev, next));
        return prev;
    }

3.AtomicMarkableReference

The AtomicMarkableReference class associates a single boolean with a reference. For example, this bit might be used inside a data structure to mean that the object being referenced has logically been deleted.

AtomicMarkableReference.boolean可用于数据结构内部表示对象是否被删除。

这里的根本在于多一个boolean Mark标记，用来标识数据对象reference是否已经更改过。

    public AtomicMarkableReference(V initialRef, boolean initialMark) {
        pair = Pair.of(initialRef, initialMark);
    }

    private static class Pair<T> {
        final T reference;
        final boolean mark;
        private Pair(T reference, boolean mark) {
            this.reference = reference;
            this.mark = mark;
        }
        static <T> Pair<T> of(T reference, boolean mark) {
            return new Pair<T>(reference, mark);
        }
    }

    private volatile Pair<V> pair;

    public boolean compareAndSet(V       expectedReference,
                                 V       newReference,
                                 boolean expectedMark,
                                 boolean newMark) {
        Pair<V> current = pair;
        return
            expectedReference == current.reference &&
            expectedMark == current.mark &&
            ((newReference == current.reference &&
              newMark == current.mark) ||
             casPair(current, Pair.of(newReference, newMark)));
    }

4.AtomicStampedReference

The AtomicStampedReference class associates an integer value with a reference. This may be used for example, to represent version numbers corresponding to series of updates.

关联了整数值，该整数值可以表示关联对象更新的次数。本质上跟AtomicMarkableReference是一样的。

    private static class Pair<T> {
        final T reference;
        final int stamp;
        private Pair(T reference, int stamp) {
            this.reference = reference;
            this.stamp = stamp;
        }
        static <T> Pair<T> of(T reference, int stamp) {
            return new Pair<T>(reference, stamp);
        }
    }

    private volatile Pair<V> pair;

    public AtomicStampedReference(V initialRef, int initialStamp) {
        pair = Pair.of(initialRef, initialStamp);
    }

    public boolean compareAndSet(V   expectedReference,
                                 V   newReference,
                                 int expectedStamp,
                                 int newStamp) {
        Pair<V> current = pair;
        return
            expectedReference == current.reference &&
            expectedStamp == current.stamp &&
            ((newReference == current.reference &&
              newStamp == current.stamp) ||
             casPair(current, Pair.of(newReference, newStamp)));
    }