Overcoming Concurrent Collections in Java: Step by Step, Simplify the Complexity

php editor Strawberry takes you step by step to explore and conquer Java concurrent collections, simplifying the complex. This series of articles that explain the Java concurrent collection framework in depth will help you understand the key concepts, technical principles and best practices in concurrent programming, and help you improve your understanding and application level of Java programming.

• ConcurrentHashMap：Thread-safe hash table
• CopyOnWriteArrayList: Thread-safe ArrayList
• BlockingQueue：Thread-safe queue
• ConcurrentSkipListSet：Thread-safe skip list collection

Choose the appropriate collection type

Choosing the appropriate concurrent collection type is crucial. Consider the following factors:

• Type safety: Is it necessary to ensure the safety of the element types in the collection? For example, ConcurrentHashMap supports type safety, while Hashtable does not.
• Performance: The performance of different collection types in concurrent scenarios varies greatly. Choose the collection type that best suits your specific needs.
• Concurrency requirements: Determine what level of concurrency your application requires. Some collection types provide higher concurrency than others.

Using iterators

Concurrent collections use iterators to implement concurrent reading. An iterator is an object that allows iterating over the elements of a collection one by one. In concurrent scenarios, you need to pay attention to the following when using iterators:

• Fail-fast semantics: Iterators for concurrent collections follow fail-fast semantics. This means that if the collection is modified during the iteration, the iterator will throw a ConcurrentModificationException exception.
• Concurrency: Iterators are not guaranteed to be thread-safe when traversing collections. This means that the collection may be modified by other threads during the iteration.

Concurrent writing

Concurrent collections support concurrent writing through the following mechanisms:

• Locks: Use locks to protect writes to the collection, ensuring that only one thread can write to the collection at a time.
• Synchronizer: Use a synchronizer to coordinate concurrent access to a collection, such as AtomicInteger.

Best Practices

Follow the following best practices to maximize the performance and security of high concurrency collections:

• Use the correct collection type: Choose the appropriate collection type based on the concurrency requirements and type safety needs of the application.
• Use iterators correctly: Understand the fail-fast semantics and concurrency limitations of iterators.
• Pay attention to concurrent writes: Use locks or synchronizers to protect concurrent writes to the collection.
• Pay attention to the collection size: Avoid using too large concurrent collections, as they will cause performance overhead.

Example

The following code example demonstrates how to use ConcurrentHashMap:

import java.util.concurrent.ConcurrentHashMap;

public class ConcurrentHashMapExample {

public static void main(String[] args) {
ConcurrentHashMap map = new ConcurrentHashMap<>();

// 并发写
map.put("key1", 1);
map.put("key2", 2);

// 并发读
for (String key : map.keySet()) {
System.out.println(key + ": " + map.get(key));
}
}
}

Summarize

By understanding the basics of concurrent collections, choosing appropriate types, using iterators correctly, managing concurrent writes, and following best practices, you can effectively conquer Java concurrent collections and achieve high performance and data integrity in parallel applications.

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