What is the difference between Java concurrency and parallelism?

The distinction between Java concurrency and parallelism is as follows:

1. Concurrency refers to the ability of multiple tasks to be executed alternately within the same time period. In concurrent programming, multiple tasks can be executed in the same time period, but not necessarily at the same time. This is achieved through thread switching and scheduling, allowing multiple tasks to quickly alternate and achieve concurrency.
2. Parallelism refers to the ability to execute multiple tasks simultaneously at the same time. In parallel programming, multiple tasks can be executed simultaneously, with each task having its own processor. By using multi-core processors or distributed systems, multiple tasks can be executed simultaneously, thus improving the program’s execution speed.

In summary, Java achieves concurrency by scheduling and switching threads to alternate between multiple tasks within the same time frame, while Java achieves parallelism by utilizing multi-core processors or distributed systems to have multiple tasks executed simultaneously at the same time point.