How to solve Java concurrency synchronization exception (ConcurrencySyncException)

How to solve Java concurrency synchronization exception (ConcurrencySyncException)

Introduction:
During the development process, concurrent programming in Java is a common requirement. However, concurrent programs are prone to synchronization exceptions, such as ConcurrencySyncException. This article describes how to identify, locate, and resolve this anomaly, and provides corresponding code examples.

1. Understanding ConcurrencySyncException
ConcurrencySyncException is an exception in which data is inconsistent due to multiple threads accessing shared resources at the same time. Such anomalies may cause unexpected behavior of the program, such as memory leaks, deadlocks, etc.

2. Identify concurrency synchronization exceptions
When a ConcurrencySyncException occurs, the system usually throws exception information. Based on the exception information, we can locate the location where the exception occurred and trace the stack trace. Common exception information includes: IllegalStateException, NullPointerException, etc.

3. Common concurrency synchronization exception scenarios
The following lists several common concurrency synchronization exception scenarios and corresponding solutions.

1. Multi-thread competition, resulting in data inconsistency errors
   Sample code:

   public class ConcurrencySyncDemo {
   
    private int count = 0;
   
    public void increment() {
        count++;
    }
   
    public void decrement() {
        count--;
    }
   }

   Solution:
   Ensure thread safety by using the synchronized keyword. Modify the sample code as follows:

   public class ConcurrencySyncDemo {
   
    private int count = 0;
   
    public synchronized void increment() {
        count++;
    }
   
    public synchronized void decrement() {
        count--;
    }
   }

2. Multiple threads operate member variables of the same object at the same time
   Sample code:

   class Worker implements Runnable {
    private int count = 0;
   
    @Override
    public void run() {
        for (int i = 0; i < 1000; i++) {
            count++;
        }
    }
   }

   Solution:
   By using Java provides atomic operation classes, such as AtomicInteger, to ensure atomic operations on member variables. Modify the sample code as follows:

   import java.util.concurrent.atomic.AtomicInteger;
   
   class Worker implements Runnable {
    private AtomicInteger count = new AtomicInteger(0);
   
    @Override
    public void run() {
        for (int i = 0; i < 1000; i++) {
            count.incrementAndGet();
        }
    }
   }

4. Deadlock problem
Deadlock is another common problem in concurrent programming, which may cause the program to wait indefinitely. In order to solve the deadlock problem, we can adopt the following solutions:

1. Avoidance strategy: Minimize the use of shared resources, such as reducing the frequency of concurrent access.
2. Prevention strategy: Obtain locks in the same order to avoid circular dependencies.
3. Detection strategy: Use tools to detect deadlocks, such as using the jstack tool to check the status of threads.
4. Solution strategy: Use Lock object instead of synchronized keyword to provide more flexible lock operation.

5. Conclusion
Concurrency synchronization exceptions are common problems in Java, but by understanding the causes of exceptions and taking corresponding solutions, we can effectively avoid such exceptions. When writing concurrent programs, you should always pay attention to thread safety and choose an appropriate synchronization mechanism.

Through the introduction and sample code of this article, I hope readers will have a certain understanding of how to solve Java concurrent synchronization exceptions and can use them flexibly in practice. In actual development, strengthening our knowledge and understanding of concurrent programming can help us write efficient and bug-free concurrent programs.

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