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: Converts a reference type to a value type. 8. Math class The role of the math classProvides a range of methodologies related to scientific calculations.Common methods: Random (), floor (), ceiling (), Max (), Min (), round () 9. String class Common methods: substring (), indexOf (), lastIndexOf (), replace (), split (), Length () Random class Function: Generates a random number.Common methods: Nextint (), nextint (int), nextdouble (), nextxxx ()

enough, we recommend that you read it directly. Steven S's style is famous for its depth, so you don't have to worry about it. The flowchart in this article is also taken from references.In this article, Steven S compares five IO models:Blocking IONonblocking IOIO multiplexingSignal driven IOAsynchronous IOBecause signal driven IO is not commonly used in practice, I will only mention the remaining four IO models.Let's talk about the objec

IO Model Description:* Blocking IO blocking IO* nonblocking io non-blocking IO* IO multiplexing IO multiplexing* Signal driven IO signal driver io ()* Asynchronous IO Asynchronous IOIO Model Description:　To better understand the IO model, we need to review it in advance: synchronous, asynchronous, blocking, non-blockingWhat is the difference between synchronous (synchronous) IO and asynchronous (asynchronous) Io, what is blocking (blocking) IO and non

differences of various Io. If the English is good enough, it is recommended to read it directly. Steven S's style is famous for its depth, so you don't have to worry about it. The flowchart in this article is also taken from references. In this article, Steven s compares five Io models:Blocking IoNonblocking IoIo multiplexingSignal driven IoAsynchronous IoBecause signal driven Io is not commonly used in practice, I will only mention the remaining fo

logic, for the system, the exception should be controllable, and is easy to operation, some anomalies, there should be a way to deal with, know how to operations, so although the exception frame is very simple, However, for the whole enterprise application development, exception handling is very important, to deal with the exception will need to understand the Java exception system.This part needs to grasp the knowledge point is not many, mainly is:Abnormal system:ThrowableExceptionRuntimeExcep

First, what is IOIO is essentially a single byte of movement. The flow can be said to be the carrier and way of byte movement, it keeps moving the data to the target. All we have to do is read the data from the stream in the direction of the stream or write the data to the stream.Second, the Java support IO operation of the library class1, according to the data types are divided into two categories:(1) Byte type: InputStream and OutputStream(2) Charac

logic, for the system, the exception should be controllable, and is easy to operation, some anomalies, there should be a way to deal with, know how to operations, so although the exception frame is very simple, However, for the whole enterprise application development, exception handling is very important, to deal with the exception will need to understand the Java exception system.This part needs to grasp the knowledge point is not many, mainly is:Abnormal system:ThrowableExceptionRuntimeExcep

logic, for the system, the exception should be controllable, and is easy to operation, some anomalies, there should be a way to deal with, know how to operations, so although the exception frame is very simple, However, for the whole enterprise application development, exception handling is very important, to deal with the exception will need to understand the Java exception system.This part needs to grasp the knowledge point is not many, mainly is:Abnormal system:ThrowableExceptionRuntimeExcep

the CPU efficiency, but there is a limit. Most of the tasks that are common are IO-intensive tasks, such as Web applications. During IO-intensive task execution, About%time is spent on Io, and there is little time spent on the CPU, so it is completely impossible to improve the running efficiency by replacing the very low-speed scripting language with Python in the very fast-running C language. For IO-intensive tasks, the most appropriate language is the most efficient (least code) language, the

, so although the exception frame is very simple, However, for the whole enterprise application development, exception handling is very important, to deal with the exception will need to understand the Java exception system.This part needs to grasp the knowledge point is not many, mainly is:Abnormal system:ThrowableExceptionRuntimeExceptionErrorRuntimeException and general Exception differences, specific treatment methods, etc.12.Java IOIO in Java is

knowledge point is not many, mainly is:Abnormal system:ThrowableExceptionRuntimeExceptionErrorThe difference between runtimeexception and general Exception, the concrete treatment method and so on. 11.Java IOIO in Java is not only the file read and write so simple, but also includes the socket network read and write, and so on all the input and output operations. For example, the standard HTTP request post content reading is also an output process,

I. Io, synchronous IO, and asynchronous IOIo is the input/output in the computer, that is, input and output. Because the program and runtime data resides in memory and is executed by the CPU, an ultra-fast compute core, where the data is exchanged, usually a disk, a network, and so on, requires an IO interface.For example, you open a browser, visit the Sina homepage, the browser this program needs to get Sina's web page via network IO. The browser fir

, if the English is good enough, recommend direct reading. Stevens's style is famous in simple and simple, so don't worry about not understand. The flowchart in this article is also intercepted from the reference document. Stevens in the article compares five kinds of Io Model altogether:Blocking IOnonblocking IOIO multiplexingSignal Driven IOAsynchronous IOSince signal driven IO is not commonly used in practice, I'm only referring to the remainin

Some people think that asynchrony is not blocking, and synchronization is blocking. This is because different people have different knowledge backgrounds, and the context is not the same when discussing this problem. So, to better answer this question, let me first limit the context of this article. The background discussed in this article is the network IO in the Linux environment. The most important references in this article are Richard Stevens's "Unix®network programming Volume 1, third edit

, if the English is good enough, recommend direct reading. Stevens's style is famous in simple and simple, so don't worry about not understand. The flowchart in this article is also intercepted from the reference document. Stevens in the article compares five kinds of Io Model altogether:Blocking IOnonblocking IOIO multiplexingSignal Driven IOAsynchronous IOSince signal driven IO is not commonly used in practice, I'm only referring to the remainin

Tags: style blog http ar io os using SP forPrefaceSome of the feedback before several articles too theoretical lack of practical details, this article on more operability of the content bar.Note: This article is based on the background of MySQL, many of which are applicable to other relational databases and need some index knowledge.Optimize your goals1. Reduce the number of IOIo is always the most vulnerable to the database, which is determined by th

Label:Index, Index!!! Jianjian index for frequently queried words!! However, you cannot build indexes too much. Changes to table records, such as insert and delete, can cause indexes to reflow, increasing the burden on the database.Optimize your goals 1. Reduce the number of IOIo is always the most vulnerable to the database, which is determined by the responsibility of the database, most of the database operations more than 90% of the time is occupie

PrefaceSome of the feedback before several articles too theoretical lack of practical details, this article on more operability of the content bar.Note: This article is based on the background of MySQL, many of which are applicable to other relational databases and need some index knowledge.Optimize your Goals1. Reduce the number of IOIo is always the most vulnerable to the database, which is determined by the responsibility of the database, most of t

ObjectiveSome of the feedback before several articles too theoretical lack of practical details, this article on more operability of the content bar.Note: This article is based on the background of MySQL, many of which are applicable to other relational databases and need some index knowledge.Optimize your Goals1. Reduce the number of IOIo is always the most vulnerable to the database, which is determined by the responsibility of the database, most of

the hard disk by Pdflush, and the data is written back to the hard disk and the memory is freed by KSWAPD and Pdflush when the memory is low. Anonymous pages, anonymous pages, which belong to a process but are not associated with any files, cannot be synced to the hard disk, and the KSWAPD is responsible for writing them to the swap partition and freeing the memory when the memory is low. IO ' s Per Second (IOPS)Each disk IO request takes a certain amount of time, and this wait time is