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to shield the host operating system threading technical details, so that Java programmers do not have to care how to map the Java Language threading mechanism to the host operating system line libraries, This task is completely done by the Java virtual machine. Within the JVM, a program's multitasking is implemented through threads. When you run a Java application with a Java command, a JVM process is started. In a JVM environment, the user thread runs in the form of threads.The meaning of mult

;ContextconfiglocationParam-name> Param-value>Classpath:/conf/applicationcontext.xmlParam-value> Context-param> Listener> Listener-class>Org.springframework.web.context.ContextLoaderListenerListener-class> Listener> servlet> Servlet-name>ViewspaceServlet-name> Servlet-class>Org.springframework.web.servlet.DispatcherServletServlet-class> Load-on-startup>1Load-on-startup> servlet> servlet-mapping> Servlet-name>ViewspaceServlet-name>

Shell1) is a scripting language used on the Linux operating system, providing interfaces for user interaction with the system, similar to the command prompt in Windows, but more powerful;2) can be executed by the command line, or it can be edited as a script file;3) mainly for automation simple system or software operation task;4) Easy to configure, maintain and transplant, do not fancy execution efficiency;5) The generic Shell is a bash (GNU Bourne-again Shell) in the GNU Toolset, which is inst

directories and sort commands:Find. -type D |Sortoutput: [[email protected] test]#Find. -type D |Sort../SCF./scf/bin./scf/Doc./scf/lib./scf/service./scf/service/Deploy./scf/service/deploy/Info./scf/service/deploy/product./test3./test4./Test5./test5/Test3[[email protected] test] #实例6: Find file by size command:Find. -size +1000c-print output: [[email protected] test]#Find. -size +1000c-Print:/test4./SCF./scf/lib./scf/service./scf/service/Deploy./scf/service/deploy/product./scf/service/deploy/Inf

() directives to embed reporting code in C.Conditional branching optimizationFor conditional selection statements, conditional branching can be optimized according to the branch declaration statement before compilation, when frequent conditions often occur or rarely occur. Example:/**/if (unlikely (err)) { ...}It is important to ensure that the current conditions are set up in the vast majority, and if you judge correctly, the performance of the program will be improved, otherwise it will d

First, briefAuthentication and encryption method of SSH connectionThe SSH connection is the CS model (client-server), the client makes the connection request, the server authenticates the client, and then considers whether to accept the connection request.The theoretical basis of SSH's secure encryption method is asymmetric encryption system. In the asymmetric encryption, the common one is the RSA encryption algorithm. When using SSH, it is important to first clarify the asymmetric encryption an

according to the protocol requirements of the device. SPI Universal Device Driver Sometimes, given the variability of the devices connected to the SPI controller, the kernel is not equipped with the appropriate protocol driver, in this case, the kernel prepares a generic SPI device driver for us, which provides the user space with a control interface to control the SPI control. The specific protocol control and data transfer work is left to the user space according to the specific equipme

learn the interfaces that these three types of devices provide to us. (17) static compilation (re-download compiled Linux kernel) and dynamic compilation. The development phase is dominated by dynamic compilation (without restarting the kernel). Dynamically loaded in the same way as the module. (18) The main device number distinguishes device drivers. The secondary device number distinguishes between multiple devices created by the same driver. Common to multiple serial ports and hard disk part

1. What is BashIn Windows systems, the most common use of a graphical interface is to perform performance. Sometimes we also use DOS commands to execute commands, where DOS is a text-mode interface, and we have some DOS instructions that can be done by interacting with the kernel of the Windows system. For example, the DIR directive is similar to the LS directive in Linux. The DOS command line we use here is similar to the Linux Bash shell environment.BASH is the abbreviation for the Bourne Agai

be divided into two categories according to the stipulated content. The first class is about the organization of the device tree, such as the name of the node is composed of which characters, length, etc., the first type of specification is more basic, is the premise of understanding the second type of norms. The second type of specification is about the contents of the device tree, such as how multicore CPUs are described, and the second type of specification can be seen as a specific applicat

red output Hello world. 　　2. Define the script:A, create a hello.sh text file;b, and then start with #!/bin/bash, where the declaration of the script must be added.c, output instructions. The # in the instruction indicates the meaning of the comment.Cases:#!/bin/bash#myFirst program! Echo " \e[1;31mhello wolrd\e[0m"　　3. Execute scriptA. Execute scripts directly using bash hello.sh, but this is inconvenient and the advantage is that you do not need to give script execution permissions.B

can now be ported to other Unix-like systems: both Linux and System V variants support sockets. The above communication mechanism will be described in detail.Attached 1: reference [2] provides a summary of the processes in the Linux environment:In general, the processes under Linux contain several key elements: There is an enforceable procedure; There is a dedicated system stack space; The kernel has its control block (Process Control block), which describes the resources

.//Cin,cout Need# include//Vectot Need# include//The accumulate algorithm requires# includeusing namespacestd;intMainvoid) {vectorint>v;//defines a vector container of vectors for(inti =0; I Ten; i++ ) { //Use the extension of the tail element to assign a valueV.push_back (i); } Vectorint>::iterator it;//use iterator iterators to traverse all elements sequentially for(it = V.begin (); It! = V.end (); it++ ) { //the value of the element at the current position of the o

module, the stronger the cohesion, the less the external, the better the module independence.Cohesion: That is, the inside of the module is designed to be more single, better. This change, the responsibility is clear.Outreach: The less the connection between the modules, the better, the connection means dependence, the lack of connectivity, the independence of the module is good, independence means that the module can be modified independently of the outside world. Reducing the outreach also in

more slowly than memory, disk I/O can become a bottleneck for the system if you wait for disk I/O to complete before doing anything else in the program. 2. Network operation: Due to the uncertainty of the network environment, if you want to read and write network data, it may be slower than disk I/O. 3.CPU: If the program is heavily consuming CPU resources for a long time, the contention for the CPU will cause performance problems, and the program needs to be rewritten to improve the situation.

: From inheritance, the simple point is that the parent class refers to the object of the subclass, the runtime still shows the behavior characteristics of the subclass, that is, the same type of object execution of the same method, may show a variety of behavior characteristics; In addition, abstraction is also an important feature, abstract is that we only need to focus on the current topic related aspects and ignore irrelevant aspects, such as the display, we said that the properties are

transaction is changed after another matter.The official document says that meeting the four characteristics of the above-mentioned business is calledACIDtransactions, wherea:atomicity,C:Consistency,I:Isolation,D:Durability). But in satisfyingACIDattributes, people take into account that performance issues are a flexible strategy. such as the isolation level of data, people can prescribe more lenient or stricter rules than before. (Refer to Wikipedia's "transaction isolation" entry for details.

on the anchor Point and coordinate point to split the image, get the 0/1 value within each point, and construct a new QR code image.However, from the image to establish a coordinate system, you can find that the picture is actually not a real square, and even a rectangle is not up, can not be scaled to restore the square, from the two-dimensional code left and right side length and the length of the red box to be seen, the left segment length is shorter than the side line, So it's not even a pa

The C language was invented in 1972 and was first used to rewrite the Uinx operating system (Unix was written primarily in assembly language, which laid the foundation of the operating system) With the success of Unix operating system, C language has been greatly promoted, has been used in large, medium and small, micro-host, is still the world's most popular, the most widely used high-level programming language One C language is a process-oriented language, non-object-or

(repeatable, can be found by index, similar List Collection "Difference: here is Key index instead of a numeric index ") Iv. How to access the elements? Set , depending on the element itself List , depending on the index of the element Map , according to Key to access the corresponding value Related articles:a big wave of Java Strikes (vi) collection and iterator interface of the--java collectiona big wave of Java Attack (vii) set interface of--java seta big wave of Java At