相当于指针。JDK8只能根部类用, JDK11可以直接用 操作内存 allocateMemory putXX freeMemory pageSize 生成类实例 allocateInstance 操作类或实例 objectFieldOffset getInt getObject CAS compareAndSwapObject() # JDK1.8 compareAndSetObject() weakCompareAndSetObject() # JDK11