National Top 10 large software company database pen questions, share to everyone

1) What is the difference between the wait and sleep methods in a Java thread?

2) What is the difference between truncate and delete?

3) say some of the commonly used classes, packages, interfaces, please give 5

4) Does the array have the length () method? Does string have the length () method?

5) What is the meaning of the left join in the database and where is it applied?
　　
6) What is the difference between iterator and listiterator?

7) If the object's reference is set to NULL, will the garbage collector immediately release the memory occupied by the object?

8). What is the structure of the Java heap like? What is the permanent generation in the heap (Perm Gen space)?

9) Tell me about your index (structure of index, impact on DML, impact on query, why query performance is improved)

What are the parts of Oracle database performance optimization?

National Top 10 large software company database pen questions, share to everyone