Question of hanging the interviewer

1. What is lexical analysis in compilation principle , What is grammatical analysis , What is recursive descent algorithm ？ How to improve compilation speed and performance

2. In the process of object instantiation , What changes have taken place in the memory and storage of the computer ？

3. Why do I need a subnet mask , Can we not use it ？

4. How to store floating-point types in memory ？

5.jvm How to set the size of threads ？

6.