Questions:

Q1: What the difference between Process and Thread ?

A1: Processes have different memory space but Threads within a process share same memory. In JVM process has at least one thread which called main thread.

Q2: How Process be created ?

A2: fork

Q3: How Thread be created ?

A3: When a JVM starts, it will creates a process and a single thread in it, which calls the main thread. And it runs main method of desingated class immediately.

procedure
Thread.start() –> nativeCreate –> java_lang_thread.Thread_nativeCreate –> thread(art/runtime).CreateNativeThread –> JNIEnvExt::Create –> pthread_create
Either JNIENVExt::Create or pthread_create failed, a OutOfMemory runtime exception will be through

Q4: How does Thread run code in it ?

A4: There is only one thread the main thread, the main static method will be run in it.

Q5: How does ActivityThread run in thread ?

When ActivityThread’s main method be invoked, there is an only main thread, it will be run in this thread.

Q6: How threads communicate with each other ?

Q7: How Android create thread ?

A7:

Q8: How processes communicate with each other(IPC) ?

Q9: How does pthread_create work ?