Java Down transformation

1.Java in the parent class directly to the subclass transformation of the illegal, can compile but run the times wrong.

The Java sub-class is legitimate to transform directly to the parent class, but after the transformation, the methods that can be executed are only available in the parent class, and when executed, the child class is defined, executed, and not executed in the parent class.

2.JVM JIT compiler, compile hotspot code for the machine code can be executed directly, improve the efficiency of program execution; it is single-threaded, daemon.

3.MySQL two kinds of common storage engine for InnoDB and MyISAM, what are the characteristics of each?

4. What is a virtual machine stack and what is a heap?

Virtual machine stack is thread-private, save local variable table, operand stack, dynamic link, method exit, etc., heap is thread-shared, Save object information (hash code specified in object header, thread private lock, lock state identity, bias thread ID, GC generational age, etc.);

Java Down transformation