Java Multithreaded Learning Notes

Concept part:

1. Concurrency and Parallelism differences:

Concurrency (Concurrency): One processor "simultaneously" handles multiple tasks

Parallel (Parallelism): multiple processors "simultaneously" Handle multiple tasks

2. Advantages and disadvantages of multithreading:

Advantages of Multithreading:

Tasks can be processed in parallel, reducing the wait time for individual tasks

A thread is less expensive than a process or sub-process system

Easier sharing of resources between threads

Leverage CPU resources in multi-core scenarios

Disadvantages of Multithreading: Access violation lock contention – Deadlock – lock granularity context switch overhead synchronization/memory copy Overhead

JVM section:

"Tinking in Java" section:

1. Concurrency has demonstrable certainty, but is actually nondeterministic.

2. If no tasks are blocked, it makes no sense to use concurrency on a single-processor machine.

3. Some programming languages are designed to isolate concurrent tasks from each other, which are often referred to as functional language--erlang.

4. Syntax sugar: while (countdown-->0), private final int id = taskcount++; The use of the rear + + and--, the counter can be added and reduced operation, convenient and clear.

5. Various actuators (Executor):

Cachedthreadpool: Generally preferred, will be created on the same number of threads as required.

Fixedthreadpool: A good thread in advance, limiting the number of threads.

　　Singlethreadexecutor is like a fixedthreadpool with a number of threads of 1 (it provides long-term survival and concurrency assurance, which is suitable for certain tasks). Singlethreadexecutor serializes all the tasks submitted to it.

6. If you want the task to return a value when it is completed, replace the Runnable interface with callable.

7.

Java Multithreaded Learning Notes