运行时数据区域—程序计数器

原創 山就在那里 2020-07-05 19:06

​ 程序计数器是一块占用内存很小的空间区域，它也是唯一 一个在《Java虚拟机规范》中没有规定任何OOM情况的区域。它就是用来记录字节码行号的。

​ Java虚拟机是支持多线程的，线程切换时就需要记录每个线程所执行到哪一行代码，此时就需要程序计数器来记录行号，以保证在线程的下次执行能够找到正确的执行位置。这也是程序计数器必须是线程私有的原因。

​ 需要说明一下：如果线程正在执行的是一个Java方法，此时程序计数器中的值为字节码的行号；如果线程正在执行的是Native方法，此时程序计数器中的值为Undefined

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