Difference Between Multithreading Multitasking, and Multiprocessing in Java

In computer science, multitasking, multithreading, and multiprocessing are all methods used to perform multiple tasks simultaneously. In this section, we will discuss the each and also discuss the differences between multitasking, multithreading, and multiprocessing in Java.

Multitasking

Multitasking is the ability of an operating system to run multiple programs or processes at the same time. This is accomplished by allowing each program or process to run for a short period of time before switching to the next one. This is known as time-sharing and allows for the efficient use of resources.

Multithreading

Multithreading, on the other hand, is a feature of a program or process that allows it to execute multiple threads at the same time. A thread is a separate flow of execution within a program or process. Each thread can run independently and has its own set of instructions, data, and resources. Multithreading is useful for tasks that can be broken down into smaller, independent parts that can be executed simultaneously.

Multiprocessing

Multiprocessing is the use of multiple processors or cores within a single computer to execute multiple tasks at the same time. This can be accomplished through the use of multiple processors or cores within a single CPU, or by using multiple CPUs in a single system. Multiprocessing is useful for tasks that require significant computational power and can take advantage of the increased number of processors or cores.

In Java, multithreading is supported by the Java Virtual Machine (JVM) and the Java language itself. The Java language provides the Thread class and the Runnable interface to create and manage threads. The JVM also provides a thread scheduler that allows multiple threads to run simultaneously on a single processor or core. Multiprocessing can also be achieved in Java by using the fork/join framework which allows to run multiple threads on multiple cores.

Example of Multitasking, Multithreading, and Multiprogramming

Example of Multitasking

Running multiple programs at the same time, such as having a web browser open while listening to music on a media player. The operating system is switching between the different programs, allocating resources to each one as needed, so that the user can interact with both at the same time.

Example of Multithreading

A program that performs multiple tasks simultaneously, such as a web server that can handle multiple requests at the same time. Each request is handled by a separate thread, allowing the server to respond to multiple requests simultaneously, rather than having to handle them one at a time.

Example of Multiprogramming

A program that utilizes multiple processors or cores to perform a task faster. An example of this could be a video rendering application that can utilize multiple cores to render a video faster than if it were only using a single core.

In Java, Multithreading can be done by creating multiple instances of the Thread class and starting them, each with its own run method, we can also create multiple instances of the Runnable interface, and pass them to the Thread constructor. In addition, multiprocessing can be achieved in Java by using the fork/join framework, which allows to run multiple threads on multiple cores.

For example, we can use the parallelStream() method in Java to divide the work of a task into multiple threads, each running on a separate core, and then combine the results of all the threads at the end.

Another example would be, in a distributed environment where you have multiple machines running the same program, each machine could be seen as a different processor working on different tasks. Multitasking, multithreading, and multiprocessing are all methods used to perform multiple tasks simultaneously, but they differ in how they accomplish this goal and the resources they utilize. Multitasking allows multiple programs or processes to run at the same time, multithreading allows a single program or process to execute multiple threads at the same time, and multiprocessing uses multiple processors or cores to execute multiple tasks at the same time.

Key Differences Between Multitasking, Multithreading, and Multiprocessing

Here is an example of a simple Java program that uses multithreading to print the numbers from 1 to 10 in two different threads:

Threadexmp.java

Output:

Thread 1: 1
Thread 1: 2
Thread 1: 3
Thread 1: 4
Thread 1: 5
Thread 1: 6
Thread 1: 7
Thread 1: 8
Thread 1: 9
Thread 1: 10
Thread 2: 1
Thread 2: 2
Thread 2: 3
Thread 2: 4
Thread 2: 5
Thread 2: 6
Thread 2: 7
Thread 2: 8
Thread 2: 9
Thread 2: 10

Note: Since each thread has its own flow of execution, it is possible that the numbers will be printed in a different order each time the program is run

The program creates two threads, "Thread 1" and "Thread 2", which both run instances of the same ThreadExample class that implements the Runnable interface. The run() method of this class simply prints out the numbers from 1 to 10, along with the name of the thread that is currently executing.

The main() method of the Main class creates two threads, passing in instances of the ThreadExample class as well as giving them a name. The start() method is called on each thread, which causes them to begin executing their respective run() methods.

Since each thread has its own flow of execution, it is possible that the numbers will be printed in a different order each time the program is run. It is also worth noting that this program is not using the fork/join framework, it's a simple example of creating two threads and starting them. If you want to use the fork/join framework you should use the Executor framework, or the parallelStream method to divide the work of a task into multiple threads and combine the results at the end.

Multitasking is a feature of the operating system and not a programming construct, it can't be done by a single program. However, you can use multiple programs or processes to accomplish multitasking. For example, you can open multiple programs or processes at the same time, such as a text editor, a web browser, and a media player, and the operating system will switch between them, allocating resources to each one as needed, so that you can interact with all of them at the same time. You can also write a program that starts multiple processes, each one is running a different task, but that's not multitasking, that's multiprocessing.