Synchronized Blocks for Better Control

Welcome back to your journey through Java concurrency! In the previous lesson, we discussed synchronization and data sharing between threads. You learned how to use the synchronized keyword to prevent race conditions and ensure the integrity of shared data by applying it to instance methods. Today, we will dive deeper by exploring synchronized blocks, which offer more granular control over specific parts of your code.

In this lesson, you will:

• Understand the four types of synchronization: instance methods, static methods, synchronized blocks inside instance methods, and synchronized blocks inside static methods.
• Learn how synchronized blocks provide more precise control over thread synchronization.
• Compare synchronized methods to synchronized blocks.
• Use practical examples to effectively apply these concepts.

By the end of this lesson, you will be able to use synchronized blocks to improve performance and manage concurrency issues in your multithreaded Java applications.

The synchronized keyword can be applied to four different parts of your code:

1. Instance Methods: Synchronizing an entire instance method ensures that only one thread can call that method at a time on the given instance.
   Java

   public synchronized void increment() {
       count++;
   }

2. Static Methods: Synchronizing a static method locks the entire class, preventing multiple threads from accessing that static method simultaneously.
   Java

   public static synchronized void staticMethod() {
       // Critical section
   }

3. Synchronized Blocks Inside Instance Methods: Synchronizing specific parts of an instance method gives you control over which code blocks need to be locked, providing more efficiency.
   Java

   public void increment() {
       synchronized (this) {
           count++;
       }
   }

4. Synchronized Blocks Inside Static Methods: You can also use synchronized blocks within static methods, which can lock specific parts of the static method.
   Java

   public static void staticMethod() {
       // Synchronize on the class itself to ensure that this block is 
       // accessed by only one thread at a time across all instances
       synchronized (SynchronizedBlockCounter.class) {
           // Critical section
       }
   }

In the previous lesson, we focused on instance methods by marking the entire method with the synchronized keyword. In this lesson, we will focus on synchronized blocks, which allow more precise control by synchronizing only the critical sections of a method rather than the entire method.