What are the characteristics of multithreaded programming languages

What is meant by threading in java? What is meant by multithreading? What are the characteristics of multithreading

In Java, a Thread is a path of program execution, an entity within a process.Threads in Java are lightweight and can run multiple threads at the same time, which is called Multithreading.

Multithreading is the simultaneous running of multiple threads in a program, each of which can perform a different task independently. Features of multithreading include:

Improving program concurrency: multithreading allows a program to perform multiple tasks at the same time, increasing the concurrency of the program and thus improving its efficiency.

Improving program responsiveness: multithreading allows a program to perform time-consuming operations without blocking, thus improving program responsiveness and enabling users to get feedback faster.

Multi-threading allows programs to fully utilize CPU resources and increase CPU utilization, thus improving program efficiency.

Easy to handle complex tasks: Multithreading allows programs to handle multiple complex tasks at the same time, thus facilitating the handling of complex tasks.

It should be noted that multi-threading can also bring some problems, such as thread safety issues, deadlock issues, etc., so you need to pay attention to these issues when writing multi-threaded programs.

What is Multithreaded Programming

Multithreaded programming technique is an important feature of the Java language. Multithreaded programming means dividing a program task into several parallel subtasks. Especially in network programming, you will find many functions that can be executed concurrently. For example, if the network transmission speed is slow and the user input speed is slow, you can use two separate threads to accomplish these two functions without affecting the normal display or other functions.  Multi-threaded is compared with single-threaded, ordinary Windows using a single-threaded program structure, the principle of operation is: the main program has a message loop, constantly read from the message queue to decide what to do next, generally for a function, only when the function is executed, the main program can receive another message to execute. For example, if a subfunction reads network data or a file, the main program can’t receive the next message until it finishes reading the data or the file. You can’t do anything during the execution of this subfunction. But often read network data and wait for user input there is a lot of time in the waiting state, multi-threading to take advantage of this feature will be divided into multiple concurrent tasks, you can solve this problem.  Thread class in Java 1. Extend the java.lang.Thread class and use it to override the run method of the Thread class.  2. Generate classes that implement the java.lang.Runnable interface and associate other instances with java.lang.Thread instances.  The Thread class is the primary class responsible for providing threading support to other classes. To use a class with threading functionality, simply derive a subclass from the Thread class in Java to extend the Thread class, e.g., printThread.java. The most important method of the Thread class is the run method. run is the method by which a new thread is executed. method, so when generating a subclass of java.lang.Thread, it must have a corresponding run method. //PrintThread.javapublicclassPrintThreadextendsThread/// Inherits the Tread class privateintcount=0/// Defines a count variable for counting the number of times a print is made and shares the variable publicstaticvoidmainStringargs//main method start PrintThreadp=newPrintThread///create a thread instance p.start///execute the thread for{;;}///main thread main method performs a loop, for performs a dead loop count ++System.out.printcount+″:Main\n″//Main thread prints the value of the count+”main” variable with a new line publicvoidrun//Thread class must have the run () method for{;;;}count++ System.out.printcount+″:Thread\n″ The above program is inheriting java.lang.Tread and overriding the run method. Tread and overrides the run method. When you start the program with the Java Virtual Machine, the program generates a thread and calls the main method of the program’s main class. The main method in this program spawns a new thread and the connection prints “Thread”. After starting the thread, the main thread continues to print “Main”.  Compile and execute this program, then immediately interrupt the program by pressing “Ctrl+C” and you will see that the two threads described above continue to print: XXX: main…. .XXX:Thread….XXX represents the number, which is the value of count above. In the author’s machine, different moments of these two threads to print a different number of times, the first print 20 main (that is, the first execution of the main thread 20 times) and then printed out 50 times Thread, and then print main…… Tip: In order to facilitate the view of the results of the execution of this program, you can import the results of the implementation of a text file, and then open this file to view the execution of each thread. Such as running: javacPrintThread.javaJavaPrintThread1.txt The first command javacPrintThread.java is to compile the java program, and the second is to execute the program and import the results into the 1.txt file. Of course you can directly execute the command: java

What is threading (multithreading) and the benefits of Python multithreading

Almost all operating systems support running multiple tasks at the same time; a task is usually a program, and each running program is a process. When a program is running, it may contain multiple streams of sequential execution internally, each of which is a thread.

Threads and processes

Almost all operating systems support the concept of processes, and all running tasks usually correspond to a process. A program becomes a process when it enters memory and runs. A process is a program that is in the process of running and has certain independent functions. A process is an independent unit of the system for resource allocation and scheduling.

Generally speaking, a process contains the following three characteristics:

Independence: a process is an independently existing entity in the system, which can have its own independent resources, and each process has its own private address space. A user process cannot directly access the address space of another process without the permission of the process itself.

Dynamic: The difference between a process and a program is that a program is just a static collection of instructions, while a process is a collection of instructions that are being active in the system. The concept of time has been added to processes. Processes have their own life cycle and various different states, which are not available in programs.

Concurrency: multiple processes can execute concurrently on a single processor and multiple processes do not affect each other.

Concurrency and parallelism are two concepts, parallelism means that at the same moment there are multiple instructions on multiple processors executing at the same time; concurrency is only aimed at the same moment there can only be a single instruction to execute, but multiple process instructions are quickly rotated to make the effect of multiple processes executing at the same time in the macro.

Most operating systems support concurrent execution of multiple processes, and almost all modern operating systems support simultaneous execution of multiple tasks. For example, a programmer is writing a program with a development tool open and a reference manual on standby, while also using the computer to play music …… In addition to this, there are a large number of underlying supportive programs running on each computer when it is running …… These processes appear to be working at the same time.

But the truth of the matter is that for a CPU, it can only execute one program at a given point in time. That is, only one process can be running, and the CPU constantly rotates execution between these processes. So why doesn’t the user feel any interruptions?

This is because the CPU is executing too fast for human perception (and if enough programs are started, the user can still feel a decrease in program speed). So while the CPU rotates between multiple processes, the user feels as if there are multiple processes executing at the same time.

Modern operating systems support concurrent execution of multiple processes, but the implementation details may vary depending on the hardware and operating system. Some of the more commonly used strategies are:

Shared multitasking, which is used by Windows 3.1 and MacOS9, for example, and preemptive multitasking, which is more efficient and is used by most current operating systems, such as Windows NT, Windows 2000, and UNIX/Linux, for example. Linux and other operating systems.

Multithreading, on the other hand, extends the concept of multiprocessing, allowing the same process to concurrently handle multiple tasks at the same time. A Thread, also known as a LightweightProcess, is the execution unit of a process. Like processes in an operating system, threads are independent, concurrent streams of execution in a program.

The main thread is created when the process is initialized. For the vast majority of applications, only one main thread is usually required, but it is also possible to create multiple sequential streams of execution within the process, which are threads, each of which is independent.

Threads are an integral part of a process; a process can have multiple threads, and a thread must have a parent process. A thread can have its own stack, its own program counter, and its own local variables, but it does not own system resources; it shares all the resources owned by the parent process with the other threads in that process. Because multiple threads share all the resources in the parent process, it is easier to program; however, more care must be taken to ensure that threads do not interfere with other threads in the same process.

Threads can accomplish certain tasks, share shared variables and parts of the environment of the parent process with other threads, and collaborate with each other to accomplish tasks that the process is trying to accomplish.

Threads run independently and are unaware of the presence of other threads in the process. Threads run preemptively, meaning that the currently running thread may be hung at any time so that another thread can run.

One thread can create and revoke another thread, and multiple threads in the same process can run concurrently with each other.

From a logical point of view, the presence of multiple threads in an application allows an application to have multiple executing parts executing at the same time, but the operating system is not required to view multiple threads as multiple independent applications, to implement scheduling and management of multiple threads, and to allocate resources. The scheduling and management of threads is done by the process itself.

In short, a program runs with at least one process, and can contain multiple threads within a process, but must contain at least one main thread.

In summary it can be said that the operating system can perform multiple tasks at the same time, each of which is a process, and processes can perform multiple tasks at the same time, each of which is a thread.

Benefits of Multi-Threading

Threads are separate, concurrent streams of execution in a program. Threads in a process are less isolated from each other than separated processes, and they share memory, file handles, and other state that should be available to the process

Because the threads are divided on a smaller scale than the processes, it makes multithreaded programs highly concurrent. Processes have separate memory units during execution, while multiple threads share memory, thus greatly improving the efficiency of the program’s operation.

Threads have higher performance than processes due to the fact that threads in the same process have in common multiple threads share the virtual space of the same process. The environment shared by threads includes process code snippets, public data of the process, etc. Using this shared data, it is easy for threads to communicate with each other.

While the operating system has to allocate separate memory space for the process and allocate a large number of associated resources when creating a process, creating threads is much simpler. As a result, using multiple threads to achieve concurrency is much more performant than using multiple processes.

To summarize, programming with multithreading has several advantages:

Memory cannot be shared between processes, but it is very easy to share memory between threads.

When the operating system creates a process, it needs to reallocate system resources for that process, but it is much less expensive to create threads. Therefore, using multiple threads for concurrent execution of multiple tasks is more efficient than using multiple processes.

The Python language has built-in support for multithreading functionality, rather than simply serving as a scheduling method for the underlying operating system, which simplifies multithreaded programming in Python.

In real-world applications, multithreading can be very useful. For example, a browser must be able to download multiple images at the same time; a web server must be able to respond to multiple user requests at the same time; and graphical user interface (GUI) applications need to start separate threads to collect user interface events from the host environment. …… In short, multithreading is very useful in real-world programming.

What does polymorphism mean in programming? What is multithreading?


Polymorphism literally means “multiple states”. In object-oriented languages, multiple different implementations of an interface are polymorphism. To quote Charlie Calverts description of polymorphism – polymorphism is the technique that allows you to set a parent object to be equal to one or more of its children, so that after assignment, the parent object can function differently depending on the characteristics of the children currently assigned to it (from “Inside Delphi 4 Programming Techniques”). In a nutshell, it’s a phrase: pointers of subclass types are allowed to be assigned to pointers of parent types. Polymorphism is implemented in both ObjectPascal and C++ through VirtualFunction.


is the technique that allows a parent object to be set equal to one or more of its children, such as Parent:=Child; polymorphism makes it possible to utilize pointers of the same class (base class) type to refer to objects of different classes, as well as to perform the same operations differently depending on the object being referenced.

Edit What is multithreading?

In computer programming, a fundamental concept is the control of multiple tasks simultaneously. Many programming problems require that a program be able to stop the task at hand, work on some other problem instead, and return to the main process. This can be accomplished in a number of ways. In the beginning, programmers who had mastered the low-level language of the machine wrote “interrupt service routines” in which the main process was suspended by hardware-level interrupts. While this was a useful approach, the resulting programs were difficult to port, creating another type of costly problem. Interrupts are necessary for tasks that are very real-time. For many other problems, however, it is only required to divide the problem into independently running program fragments so that the program as a whole can respond more quickly to user requests. In the beginning, threads were simply a tool for allocating processing time to a single processor. But if the operating system itself supports multiple processors, then each thread can be assigned to a different processor, truly entering a state of “parallel computing”. From a programming language perspective, one of the most valuable features of multithreaded operations is that the programmer doesn’t have to worry about how many processors are being used. The program is logically divided into threads; if the machine itself has more than one processor installed, the program will run faster without any special tuning. Based on the previous discussion, you may feel that thread processing is very simple. However, there is one issue that must be taken into account: shared resources! If there are multiple threads running at the same time and they are trying to access the same resources, a problem is encountered. As an example, two processes cannot send a message to a printer at the same time. To solve this problem, for those resources that can be shared (like printers), they have to go into a locked state for the duration of their use. So a thread can lock a resource and then, after completing its task, unlock (release) the lock so that other threads can then use the same resource. Multithreading is for synchronizing multiple tasks, not to improve operational efficiency, but to improve the efficiency of the system by increasing the efficiency of resource usage. Threads are implemented when multiple tasks need to be completed at the same time.