Method and Block Synchronization in Java

In Java, there are two ways to synchronize access to shared resources: method synchronization and block synchronization.

Method synchronization involves using the synchronized keyword to mark an entire method as synchronized. This means that only one thread can execute the method at a time. Here's an example:

public class Counter {
  private int count;
  public synchronized void increment() {
    count++;
  }
  public synchronized void decrement() {
    count--;
  }
  public synchronized int getCount() {
    return count;
  }
}
​

In this example, the increment(), decrement(), and getCount() methods are all marked as synchronized. This ensures that only one thread can access the count variable at a time, preventing race conditions and ensuring data consistency.

Block synchronization involves using the synchronized keyword to mark a block of code as synchronized. This allows you to synchronize access to a specific section of code rather than an entire method. Here's an example:

public class Counter {
  private int count;
  public void increment() {
    synchronized (this) {
      count++;
    }
  }
  public void decrement() {
    synchronized (this) {
      count--;
    }
  }
  public int getCount() {
    synchronized (this) {
      return count;
    }
  }
}​

In this example, we use block synchronization to synchronize access to the count variable within each method. We use the synchronized keyword to create a synchronized block of code, and pass this as the monitor object. This ensures that only one thread can access the block of code at a time, preventing race conditions and ensuring data consistency.

Method synchronization and block synchronization both serve the same purpose: to synchronize access to shared resources in a multithreaded environment. The choice between them depends on the specific requirements of your application and the design of your code. In general, method synchronization is simpler and more convenient, but block synchronization provides finer-grained control over access to shared resources.