What is Synchronization in Respect to Multi-Threading in Java

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With respect to multi-threading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one Java thread to modify a shared variable while another thread is in the process of using or updating same shared variable. This usually leads to erroneous behavior or program.

In the context of multi-threading in Java, synchronization refers to the coordination of multiple threads to ensure that they access shared resources or critical sections of code in a controlled and orderly manner. The primary goal of synchronization is to prevent data corruption or inconsistent results that may occur when multiple threads concurrently access and modify shared data.

Java provides several mechanisms for synchronization, and the two most common ones are:

  1. 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 intrinsic lock for that method’s object, preventing other threads from executing synchronized methods on the same object concurrently.
    java
    public synchronized void synchronizedMethod() {
    // Synchronized code block
    }
  2. Synchronized Blocks:
    • You can use synchronized blocks to explicitly specify a section of code that should be executed by only one thread at a time. This is done by surrounding the critical section of code with the synchronized keyword followed by an object reference, which serves as the lock.
    java

    Object lock = new Object();

    // …

    synchronized (lock) {
    // Synchronized code block
    }

Synchronization helps in preventing race conditions and ensures the consistency of shared data by allowing only one thread to access the synchronized code block or method at a time. It helps in maintaining thread safety and avoiding issues like data corruption or unexpected behavior in a multi-threaded environment.