类图：

源码： 

package java.util.concurrent.atomic;import java.util.function.UnaryOperator;import java.util.function.BinaryOperator;import sun.misc.Unsafe;//原子变量类 V:变量类型public class AtomicReference
    
      implements java.io.Serializable {    private static final long serialVersionUID = -1848883965231344442L;//版本号    private static final Unsafe unsafe = Unsafe.getUnsafe();//使用sun的Unsafe完成cas指令    private static final long valueOffset;//value内存地址相对于对象内存地址的偏移量    private volatile V value;//变量类型    static {        try {            //初始化valueOffset：通过unsafe.objectFieldOffset方法获取成员属性value内存地址相对于对象内存地址的偏移量            valueOffset = unsafe.objectFieldOffset (AtomicReference.class.getDeclaredField("value"));        } catch (Exception ex) { throw new Error(ex); }    }    //构造方法:value为null    public AtomicReference() {    }    /**     * 构造方法，传入指定V值     */    public AtomicReference(V initialValue) {        value = initialValue;    }    /**     * 获取v值     */    public final V get() {        return value;    }    /**     * 设为指定值     */    public final void set(V newValue) {        value = newValue;    }    /**     * 最终设为指定值，但其它线程不能马上看到变化，会延时一会     */    public final void lazySet(V newValue) {        unsafe.putOrderedObject(this, valueOffset, newValue);    }    /**     * CAS操作，现代CPU已广泛支持，是一种原子操作；     * 简单地说，当期待值expect与valueOffset地址处的值相等时，设置为update值     */    public final boolean compareAndSet(V expect, V update) {        return unsafe.compareAndSwapObject(this, valueOffset, expect, update);    }    //和compareAndSet()方法相同    public final boolean weakCompareAndSet(V expect, V update) {        return unsafe.compareAndSwapObject(this, valueOffset, expect, update);    }    //以原子方式设置为给定值，并返回旧值    public final V getAndSet(V newValue) {        return (V)unsafe.getAndSetObject(this, valueOffset, newValue);    }    /**     * 以原子方式设置为给定值，并返回旧值     * updateFunction 一个参数的函数     */    public final V getAndUpdate(UnaryOperator
     
       updateFunction) {        V prev, next;        do {            prev = get();            next = updateFunction.apply(prev);        } while (!compareAndSet(prev, next));        return prev;    }    /**     * 以原子方式设置为给定值，并返回新值     * updateFunction 一个参数的函数     */    public final V updateAndGet(UnaryOperator
      
        updateFunction) {        V prev, next;        do {            prev = get();            next = updateFunction.apply(prev);        } while (!compareAndSet(prev, next));        return next;    }    /**     * 以原子方式设置为给定值，并返回旧值     * accumulatorFunction 两个参数的函数     */    public final V getAndAccumulate(V x, BinaryOperator
       
         accumulatorFunction) {        V prev, next;        do {            prev = get();            next = accumulatorFunction.apply(prev, x);        } while (!compareAndSet(prev, next));        return prev;    }    /**     * 以原子方式设置为给定值，并返回新值     * accumulatorFunction 两个参数的函数     */    public final V accumulateAndGet(V x,BinaryOperator
        
          accumulatorFunction) {        V prev, next;        do {            prev = get();            next = accumulatorFunction.apply(prev, x);        } while (!compareAndSet(prev, next));        return next;    }    //返回v类的toString()方法得到的字符串    public String toString() {        return String.valueOf(get());    }}