Detailed explanation of Java thread-safe collection classes

Java provides thread-safe collection classes to solve inconsistency problems caused by multi-threaded concurrent data access, including ConcurrentHashMap (thread-safe hash table), ConcurrentLinkedQueue (thread-safe linked list), CopyOnWriteArrayList (thread-safe list) and ConcurrentSkipListSet (thread-safe list) Safety jump table). These collection classes ensure data consistency and are easy to use by providing atomic operations and good concurrency performance.

Detailed explanation of Java thread-safe collection classes

In a multi-threaded environment, when multiple threads access and modify shared data at the same time If the necessary synchronization mechanism is not adopted, data inconsistency and program errors may result. Java provides thread-safe collection classes to solve this problem.

Thread-safe collection class

• ConcurrentHashMap: A thread-safe hash table that supports concurrent access and writing.
• ConcurrentLinkedQueue: A thread-safe linked list that supports multi-threaded concurrent addition and deletion operations.
• CopyOnWriteArrayList: A thread-safe list that creates a copy of the list every time it is modified.
• ConcurrentSkipListSet: A thread-safe skip list that provides ordered element access.

Practical case: Concurrent shopping basket

Suppose we have an online shopping website and need to maintain the shopping basket of each user. In order to avoid multiple threads concurrently modifying the data of the same shopping basket, you can use ConcurrentHashMap:

import java.util.concurrent.ConcurrentHashMap;

public class ConcurrentCart {

    private ConcurrentHashMap<String, Integer> items;

    public ConcurrentCart() {
        this.items = new ConcurrentHashMap<>();
    }

    public void addItem(String itemName, int quantity) {
        items.put(itemName, items.getOrDefault(itemName, 0) + quantity);
    }

    public void removeItem(String itemName) {
        items.remove(itemName);
    }

    // ... 其他方法
}

In this ConcurrentCart class, the items dictionary is used ConcurrentHashMap to ensure thread safety. When we add or delete items, these operations are atomic and there will be no data inconsistency issues.

Advantages

• Data consistency: Avoids data inconsistency caused by concurrent access by multiple threads.
• Performance: These collection classes provide good concurrency performance and can work efficiently even in high concurrency scenarios.
• Easy to use: Simply replace the standard collection class with a thread-safe collection class to achieve thread safety.

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