Android learning notes, first known as Android .. DVM and JVM

Android is an open-source Linux-based operating system. One of the core content of Android is DVM, which is the Dalvik virtual machine. It differs from the traditional JVM:

1. Architecture differences: the former is based on Reg (in CPU), and the latter is based on stack (in memory ). The most significant difference is that the former can effectively reduce the number of memory accesses to speed upProgram.

Others, such as optimization in advance and faster compilation, cannot be understood because they do not understand the compilation principles for the time being.

2. The executed bytecode is different. The former is in Dex format and the latter is in. Class format. Dex is optimized for mobile devices.

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3. DVM can run multiple VM entities simultaneously and coexist in independent processes. What about JVM? It also exists in the independent process .. There is no deep understanding yet .. To be supplemented later.

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4. DVM uses the Linux system to manage processes and threads. Because a thread in DVM is a thread in Linux, it depends on the system to manage threads.