Thread synchronization is an important concept in Java that enables multiple threads to access shared resources safely. When multiple threads try to access the same resource simultaneously, it can lead to race conditions and data inconsistencies. Thread synchronization helps to prevent these issues by allowing only one thread to access a shared resource at a time.
There are several ways to synchronize threads in Java:
Synchronized methods
A synchronized method can be called by only one thread at a time. To create a synchronized method, we can use the synchronized
keyword in the method declaration. For example:
public synchronized void printNumbers() {
for (int i = 1; i <= 10; i++) {
System.out.println(i);
}
}
Synchronized blocks
A synchronized block is a block of code that can be accessed by only one thread at a time. To create a synchronized block, we can use the synchronized
keyword followed by a block of code. For example:
public void printNumbers() {
synchronized (this) {
for (int i = 1; i <= 10; i++) {
System.out.println(i);
}
}
}
Static synchronized methods
A static synchronized method is a method that is synchronized at the class level. This means that only one thread can access the method at a time, regardless of the object that the thread is using. To create a static synchronized method, we can use the synchronized
keyword followed by the static
keyword in the method declaration. For example:
public static synchronized void printNumbers() {
for (int i = 1; i <= 10; i++) {
System.out.println(i);
}
}
The java.util.concurrent.locks
package
The java.util.concurrent.locks
package provides several classes that can be used to synchronize threads. These classes include ReentrantLock
, ReentrantReadWriteLock
, and Condition
.
Using thread synchronization is an important way to ensure that shared resources are accessed safely by multiple threads in a Java program. It helps to prevent race conditions and data inconsistencies, which can lead to unpredictable results and errors. By using synchronized methods, synchronized blocks, static synchronized methods, or the java.util.concurrent.locks
package, we can ensure that our Java program runs smoothly and correctly.