What are the common challenges in implementing thread safety in Java functions?

Java thread safety challenges include race conditions and visibility issues, which can be solved through mutually exclusive access, immutable objects, concurrent collections, and atomic variables. For example, in a bank transfer system, use the synchronized keyword to protect account balances to prevent concurrent access and keep funds safe.

Thread safety challenges in Java functions

Concurrency issues

Thread concurrency When accessing shared data, race conditions can occur, causing data inconsistencies or unexpected behavior.

Code example:

public class NonThreadSafeCounter {
    private int count;

    public void increment() {
        count++; // 线程不安全操作
    }
}

When two threads call increment() at the same time, they may read count## at the same time # value and increment it, leading to incorrect results.

Visibility issues

When one thread modifies shared memory, other threads may not see the change.

Code example:

public class VisibilityIssue {
    private boolean done = false;

    public void setDone() {
        done = true; // 可见性问题操作
    }

    public boolean isDone() {
        return done;
    }
}

One thread calls

setDone(), but another thread calls isDone() Possibly will return false because the change has not yet propagated.

Solution

To solve the thread safety challenge, the following approach can be used:

• Mutually exclusive access: Use a synchronization mechanism, such as the synchronized keyword or the ReentrantLock, to provide mutually exclusive access to shared data.
• Immutable objects: Use immutable objects, create them once and then never modify them.
• Concurrent collections: Use concurrent collections in the java.util.concurrent library, such as ConcurrentHashMap and CopyOnWriteArrayList.
• Atomic variables: Use atomic variables in the java.util.concurrent.atomic package, such as AtomicInteger.

Practical case

Design an online bank transfer system

In the bank transfer system, the account balance Concurrent access is critical. Without appropriate thread safety measures, loss of funds or duplicate transfers may result.

You can use the

synchronized keyword to protect the balance field to ensure that only one transfer is executed at a time:

public class BankAccount {
    private int balance;

    public synchronized void transfer(int amount) {
        balance -= amount;
    }
}

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