1. What is the use of thread.join()?

2. Given a sorted array of integers nums and an integer target, write a function to search target in nums. If the target exists, then return its index. Otherwise, return -1. You must write an algorithm with O(log n) runtime complexity.

3. How does ALB work?

4. What is a test case?

5. Explain how you would apply SOLID principles to design a calculator.