Shulou(Shulou.com)06/03 Report--

This article mainly introduces the Java IO-related knowledge points, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor with you to understand.

1, user space, system space

The Linux system will divide a process into two spaces, user space and system space. For example, we normally encode and operate in user space. If we need to call system functions, such as copying system files, we need to call system components, get kernel services, and complete the operation.

Two stages of IO

The execution of IO is divided into two stages, waiting for it to be ready and performing a copy

Wait ready: we know that when we perform an IO operation, the data may come from another application or network. If there is no data, the operating system will wait all the time, and the application may also wait.

Perform a copy: copy data to the application workspace

Blocking and non-blocking, synchronous and asynchronous

To talk about synchronization and non-synchronization first, the simplest thing is to see whether to start a thread or process to complete IO. When synchronizing IO, the system will stop and wait for this to be done before doing anything else, while asynchronous IO uses multithreading to start a new thread to do this, and it can do something else and wait for notice.

Let's talk about blocking and non-blocking, which are actually concerned with the state of the program while waiting for the result of the call. Blocking means that when you get the result, you will hang until you wait until the complete result. Non-blocking means that there is no blocking thread when the process cannot get the result. This is a bit of a twist, and there is a popular explanation if it is blocked. I'm going to get this thing, and in the process, I lose the CPU, and I won't get the CPU until the result, but if I'm non-blocking, I'll keep holding the CPU, and I can keep checking it.

Several IO models

At present, there are five kinds.

Blocking IO

The most traditional kind of IO, that is, blocking occurs in reading and writing.

Non-blocking IO

When a user initiates read, he will not lose CPU, but will always check. If it is not successful, an error will be returned. If a successful signal is received, a read operation will be initiated to obtain the complete result.

Multiplexing IO

This is the core of Java NIO, there will be a thread to manage the state of multiple socket, check whether it is ready, only found that really ready, will call cpu to perform IO operations, this is more important

Signal driven IO

Use less, ignore

Asynchronous IO

Start a thread to execute it.

Thank you for reading this article carefully. I hope the article "what are the knowledge points related to IO in Java" shared by the editor will be helpful to you. At the same time, I also hope that you will support us and pay attention to the industry information channel. More related knowledge is waiting for you to learn!

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