1. atomic相关类简介
atomic相关类是java.util.concurrent下提供的一系列封装了原子性操做的类，主要包括基本数据类型包装类的原子操作类，如AtomicBoolean、AtomicInteger，以及数组及其他对象的原子操作类，如AtomicReference<V>、AtomicReferenceArray<E>。
原子操作类清单
| Class | Description |
|---|---|
| AtomicBoolean | A boolean value that may be updated atomically. |
| AtomicInteger | An int value that may be updated atomically. |
| AtomicIntegerArray | An int array in which elements may be updated atomically. |
| AtomicIntegerFieldUpdater<T> | A reflection-based utility that enables atomic updates to designated volatile int fields of designated classes. |
| AtomicLong | A long value that may be updated atomically. |
| AtomicLongArray | A long array in which elements may be updated atomically. |
| AtomicLongFieldUpdater<T> | A reflection-based utility that enables atomic updates to designated volatile long fields of designated classes. |
| AtomicMarkableReference<V> | An AtomicMarkableReference maintains an object reference along with a mark bit, that can be updated atomically. |
| AtomicReference<V> | An object reference that may be updated atomically. |
| AtomicReferenceArray<E> | An array of object references in which elements may be updated atomically. |
| AtomicReferenceFieldUpdater<T,V> | A reflection-based utility that enables atomic updates to designated volatile reference fields of designated classes. |
| AtomicStampedReference<V> | An AtomicStampedReference maintains an object reference along with an integer "stamp", that can be updated atomically. |
| DoubleAccumulator | One or more variables that together maintain a running double value updated using a supplied function. |
| DoubleAdder | One or more variables that together maintain an initially zero double sum. |
| LongAccumulator | One or more variables that together maintain a running long value updated using a supplied function. |
| LongAdder | One or more variables that together maintain an initially zero long sum. |