Recent studies of the JVM, found a problem of the program counter, I don't feel very understanding, a great god to explain,


The program counter:
Bytecode interpreter to work is by changing the value of the counter to select a need to execute bytecode instruction, implement the native methods, counter is empty (undefined)


problem a:
Since this record is empty, not specific which line the line number, so how to specify the next line which is the code you need to perform a line,

problem two:
And native method and way to 1:1 to Java thread mapping, through what way to let the native and Java threads associated?

question 3:
Is there any way I can to validate the above problem?