How is synchronization within a method with the synchronized keyword implemented?

In Java, the keyword synchronized is used to ensure mutual exclusion when accessing a critical section of code.

When a method is declared as synchronized, the JVM automatically acquires the monitor (lock) of the object on which the method is called before executing the method's code, and releases it after completion.

If the method is non-static, the monitor is the current instance object (this). If the method is static, the monitor is the class object (Class object).

This guarantees that only one thread can execute this method for a given object (or class) at a time, preventing race conditions.

Example:

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

Here, if multiple threads call increment(), they will execute sequentially, not interrupting each other.