Android interview question 5

26. What will happen? How to avoid it? Can I capture exceptions that cause them?

Such as null pointer, array out-of-bounds, type conversion exception, etc.

View the location of the Code that throws an exception and modify it in the corresponding code of the program.

If it is not declared, it will throw an exception, so it is impossible to throw an exception during running. Have you ever encountered an exception? What problems will this cause? How can this problem be solved?

. I have met. For example, a null pointer exception is the most common exception, as long as a method is called. The program may fail to run normally. You can open the console to view the information, find the code segment that throws the exception information, and modify it.

Process and process application process are the same concept

Virtual Machine. Each application runs in its own process and has an independent virtual machine instance. Every process is in the process, so it can be considered the same concept.

Running an application as an independent process can prevent all programs from being shut down when the VM crashes.

And.

Is the operating system a real-time operating system?

An embedded real-time operating system can accept and process external events or data at a high speed, the processing result can control the production process or quickly respond to the processing system within the specified time, and control all real-time tasks to coordinate and operate in an embedded operating system. It is mainly used for industrial control, military equipment, aerospace and other fields with demanding system response time requirements, which requires the use of real-time systems. It can be divided into two types: Soft Real-time and hard real-time, but kernel-based. It can be preemptible in user space, and kernel space can be preemptible in the future. It is strictly a soft real-time system.

Real-time. The common requirement for embedded real-time operating systems is that the system can respond to events quickly and has a strong real-time performance. Therefore, the kernel of embedded real-time operating systems can be preemptible.
Scalability. The embedded operating system runs on a variety of hardware platforms, and its host objects are even more varied. Therefore, various functional modules provided in the embedded operating system are required for users to choose and use as needed, that is, it is required to have good scalability.
High reliability. Embedded systems are widely used in military weapons, aerospace, transportation, and important production fields. Therefore, embedded operating systems must have high reliability, necessary fault tolerance and error prevention measures should be provided for key and critical applications to further improve system reliability.
Portability. To adapt to a variety of hardware platforms, embedded operating systems should be able to run stably on different platforms without a large number of modifications.

1. Page-based storageThe logical address in the management consists of a page number and an industry address, but the job still uses a continuous logical address, which can be viewed as a one-dimensional (linear) Address structure. The user does not have the paging concept. The operating system only paging the job information when it is loaded into the primary storage according to the block length. Segmented StorageThe logical address in management consists of the segment number and the segment address. It supports user segmentation. The logical addresses in each segment are continuous, while the logical addresses between segments are discontinuous. Therefore, the logical address in the Segment Storage Management is actually a two-dimensional address structure.