Java Thread Pool Concurrency Programming Guide

How to use thread pool To use thread pool you need to follow the following steps:

1. Create Thread pool object.
2. Submit the task to the thread pool.
3. Close the thread pool.

Thread Pool Factory The thread pool factory is a factory class that creates thread pool objects, which allows customizing the behavior of the thread pool, such as the number of threads, queue length, and task rejection policy.

Core threads and maximum threads Core threads are threads that are always active, they are not destroyed when idle. Max threads is the maximum number of threads that can be created when the task queue is full.

queue Task queue is used to store tasks waiting to be executed. It can be a blocking queue or an unbounded queue. A blocking queue prevents tasks from being added until a thread is available, while an unbounded queue allows unlimited tasks to be added.

Task rejection policy When the task queue is full and the number of threads reaches the maximum value, the thread pool will implement a task rejection policy to process new tasks. Common strategies include:

• AbortPolicy: Throws RejectedExecutionException.
• CallerRunsPolicy: The task is executed by the calling thread.
• DiscardOldestPolicy: Discard the oldest task in the queue.
• DiscardPolicy: Discard the new task.

Monitoring thread pool Monitoring The thread pool is critical to ensure its proper operation and performance optimization. Indicators that can be monitored include:

• Thread pool size
• Task queue size
• Number of active threads
• execution time

Best Practices

• Use the appropriate number of threads: avoid over or under.
• Use a reasonable task queue size: avoid queues that are too large, causing memory consumption and delays.
• Choose an appropriate task rejection policy: Choose based on application requirements.
• Monitor thread pool metrics: identify potential issues and make adjustments.
• Avoid performing long-term blocking operations in tasks: use asynchronous operations or queue mechanisms.
• Close the thread pool appropriately: Make sure all tasks are completed to avoid resource leaks.

advantage

• Performance optimization: By reusing threads, the overhead of frequently creating and destroying threads is avoided.
• Concurrent processing: Allows multiple tasks to be processed at the same time, improving application throughput.
• Thread management: Provides a way to centrally manage threads and simplify parallel programming.
• Resource Limitation: By controlling the number of threads and queue length, you can prevent applications from excessively consuming resources.

shortcoming

• Thread leak: If the thread pool is not closed correctly, thread leakage may occur.
• Task Delay: If the task queue is full, new tasks may be delayed in execution.
• Complex configuration: OptimizationThe thread pool requires understanding its configuration options and impact on performance.

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