What is synchronization and why is it important?

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With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object’s value. This often leads to significant errors.

In the context of Core Java, synchronization refers to the coordination of multiple threads to control their access to shared resources. When multiple threads are executing concurrently, there is a possibility of data corruption or unexpected behavior if they access shared resources simultaneously. Synchronization helps in preventing such issues by ensuring that only one thread can access the shared resource at a time.

Key concepts related to synchronization in Java include:

  1. Mutual Exclusion: Synchronization ensures that only one thread can access a critical section of code or a shared resource at a time. This prevents multiple threads from interfering with each other, reducing the chances of data corruption.
  2. Visibility: Synchronization also addresses the issue of visibility, ensuring that changes made by one thread to shared data are visible to other threads. Without synchronization, there is a risk of one thread not seeing the latest changes made by another thread.
  3. Atomicity: Synchronization helps in achieving atomicity, meaning that a series of operations on shared data appears as a single, indivisible operation. This is important to maintain data consistency.

Java provides two main ways to achieve synchronization:

  • Synchronized Methods: You can use the synchronized keyword to declare a method as synchronized. When a thread invokes a synchronized method, it automatically acquires the lock for that method’s object, preventing other threads from executing synchronized methods of the same object concurrently.
    java
    public synchronized void synchronizedMethod() {
    // Synchronized code block
    }
  • Synchronized Blocks: You can use synchronized blocks within methods to explicitly define a critical section. This allows more flexibility in controlling which part of the code is synchronized.
    java
    public void someMethod() {
    // Non-critical section    synchronized (lockObject) {
    // Synchronized code block (critical section)
    }

    // Non-critical section
    }

Synchronization is essential in multithreading scenarios to prevent race conditions, data inconsistencies, and other concurrency issues. It ensures that the execution of threads is properly coordinated, maintaining the integrity of shared data and overall program correctness. However, it’s worth noting that improper use of synchronization can lead to problems like deadlocks and reduced performance, so it should be applied judiciously.