深入浅析java 中volatile与lock的原理

The Java programming language allows threads to access shared variables (§17.1). As a rule, to ensure that shared variables are consistently and reliably updated, a thread should ensure that it has exclusive use of such variables by obtaining a lock that, conventionally, enforces mutual exclusion for those shared variables.The Java programming language provides a second mechanism, volatile fields, that is more convenient than locking for some purposes.A field may be declared volatile, in which case the Java Memory Model ensures that all threads see a consistent value for the variable .It is a compile-time error if a final variable is also declared volatile.