Introduction to Synchronize in Java
Java is a prominent computer language that was developed in 1995. Oracle owns it, and it is used by over 3 billion devices. In Java, synchronization is the ability to regulate multiple threads’ access to a shared resource. Multiple threads attempt to access shared resources at the same time under the Multithreading concept, resulting in inconsistent outcomes. In Java, Inheritance is also considered an important concept. Synchronize in Java is required for thread-to-thread communication to be reliable. Java is used for the following:
- Applications for mobile devices (especially Android apps)
- Applications for the desktop,
- Web-based apps,
- Application servers and web servers,
- Connection to the Games Database.
Also Read : Major Difference between Comparable vs Comparator Java
Why Should You Use Java?
- Java runs on a variety of systems (Windows, Mac, Linux, Raspberry Pi, etc.)
- It is one of the world’s most popular programming languages. It is simple to understand and apply.
- It is open-source and free to use.
- It is safe, quick, and strong.
- It has a lot of community backing (tens of millions of developers)
- Java is an object-oriented programming language that offers programs a clear structure and allows code to be reused, saving development costs.
- Because Java is similar to C++ and C#It is simple for programmers to convert to Java or vice versa.
Why do we use Synchronize in Java?
Synchronize in Java is the ability to regulate multiple processes’ access to a shared resource. Multiple threads attempt to access shared resources at the same time under the Multithreading concept, resulting in inconsistent outcomes. Synchronization is required for thread-to-thread communication to be reliable. Synchronization aids in thread interference prevention. Synchronization aids in the prevention of concurrency issues.
Synchronization Types
There are two forms of synchronization.
- Process Synchronization
- Thread Synchronization
Process Synchronization
A process is nothing more than a program in execution. It operates in a separate process that is not connected to another. The operating system allocates resources to the process, such as memory and CPU time. The phrase “process synchronization” refers to the sharing of capabilities between two or more processes while guaranteeing data consistency. The Critical Section is a piece of code that is shared by several processes in a programming language. There are various methods to prevent critical section problems, such as Peterson’s Solution, but the most famous is Semaphores.
Thread Synchronization
Thread Synchronization refers to the concurrent execution of a vital resource by two or more Threads. A thread is a subroutine that can run separately within the context of a single process.
A single process can have numerous threads, and the program can schedule all of the threads to use a vital resource. A single thread, in reality, includes numerous threads.
There are two forms of thread synchronization:
1. Mutual Exclusive:
A Mutex, also known as a Mutual Exclusive, allows only one thread to access shared resources. It will not enable simultaneous access to shared resources. It is possible to accomplish this in the following methods.
- Synchronized Method
- Synchronized block
- Static Synchronization
2. Collaboration (Inter Thread Communication in java)
Check out Adapter Class in Java for more.
Lock Concept in Java
The Lock Concept synchronizes in Java Synchronization Mechanism was created by employing the synchronized keyword in the Java programming language. It is constructed on top of the locking mechanism, which is handled by the Java Virtual Machine (JVM). The synchronize in java keyword may only be used on methods and blocks; it cannot be used on classes or variables. The synchronized keyword in Java generates a crucial section, which is a block of code. To access the crucial region, the thread must first gain the lock on the appropriate object.
A lock, like synchronized blocks, is a thread synchronization mechanism, however, locks can be more complicated than Java’s synchronized blocks. Locks (and other more complicated synchronization methods) are built with synchronized blocks, therefore we can’t get rid of the synchronizing in java keyword entirely.
Since Java 5, the package java.util.concurrent.locks has multiple lock implementations, thus you may not need to write your own locks. However, you will still need to know how to utilize them, and it may be beneficial to understand the theory underlying their implementation. See my lesson on the java.util.concurrent.locks.Lock interface for additional information.
Also Read : Differences between Python and Java
Java Synchronized Method
When we use the Synchronized keywords in a method, the method is called a Synchronized Method.
- It is used to secure an object’s access to shared resources.
- When the synchronized method is invoked, the object obtains the lock.
- The lock will not be released until the thread has finished its purpose.
Syntax:
Acess_modifiers synchronized return_type method_name (Method_Parameters) {
// Code of the Method.
}
Java Synchronized Method Example:
class Power{
synchronized void printPower(int n){//method synchronized
int temp = 1;
for(int i=1;i<=5;i++){
System.out.println(Thread.currentThread().getName() + “:- ” +n + “^”+ i + ” value: ” + n*temp);
temp = n*temp;
try{
Thread.sleep(500);
}catch(Exception e){System.out.println(e);}
}
}
}
class Thread1 extends Thread{
Power p;
Thread1(Power p){
this.p=p;
}
public void run(){
p.printPower(5);
}
}
class Thread2 extends Thread{
Power p;
Thread2(Power p){
this.p=p;
}
public void run(){
p.printPower(8);
}
}
public class Synchronization_Example2{
public static void main(String args[]){
Power obj = new Power();//only one object
Thread1 p1=new Thread1(obj);
Thread2 p2=new Thread2(obj);
p1.start();
p2.start();
}
}
Output:
Thread-0:- 5^1 value: 5
Thread-0:- 5^2 value: 25
Thread-0:- 5^3 value: 125
Thread-0:- 5^4 value: 625
Thread-0:- 5^5 value: 3125
Thread-1:- 8^1 value: 8
Thread-1: – 8^2 value: 64
Thread-1:- 8^3 value: 512
Thread-1:- 8^4 value: 4096
Thread-1:- 8^5 value: 32768
Synchronized keywords were employed in this case. It is beneficial to run only one thread at a time. It does not let another thread execute until the first one is done; when the first thread is completed, the second thread is permitted to execute. We can now view the output of powers 5 and 8 from n1 to n5. Thread-0 finished, and only Thread-1 began.
Synchronized Block
If you only wish to synchronize in java, a few lines of code in a method, a synchronized block can assist. The object will be sent as a parameter. It will function in the same way as the Synchronized Method. In the case of synchronized methods, the lock is accessed on the method, but in the case of synchronized blocks, the lock is obtained on the object.
Syntax:
synchronized (object) {
//code of the block.
}
Program to understand the Synchronized Block:
class Power{
void printPower(int n){
synchronized(this){ //synchronized block
int temp = 1;
for(int i=1;i<=5;i++){
System.out.println(Thread.currentThread().getName() + “:- ” +n + “^”+ i + ” value: ” + n*temp);
temp = n*temp;
try{
Thread.sleep(500);
}catch(Exception e){System.out.println(e);}
}
}
}
}
class Thread1 extends Thread{
Power p;
Thread1(Power p){
this.p=p;
}
public void run(){
p.printPower(5);
}
}
class Thread2 extends Thread{
Power p;
Thread2(Power p){
this.p=p;
}
public void run(){
p.printPower(8);
}
}
public class Synchronization_Example3{
public static void main(String args[]){
Power obj = new Power();//only one object
Thread1 p1=new Thread1(obj);
Thread2 p2=new Thread2(obj);
p1.start();
p2.start();
}
}
Output:
Thread-0:- 5^1 value: 5
Thread-0:- 5^2 value: 25
Thread-0:- 5^3 value: 125
Thread-0:- 5^4 value: 625
Thread-0:- 5^5 value: 3125
Thread-1:- 8^1 value: 8
Thread-1:- 8^2 value: 64
Thread-1:- 8^3 value: 512
Thread-1:- 8^4 value: 4096
Thread-1:- 8^5 value: 32768
In this case, we did not synchronize in java the entire function, but only just a few lines of code within it. We obtained the same results as the synchronized technique.
Static Synchronization
Every object synchronize in Java has a single lock (monitor) associated with it. The thread that enters the synchronized procedure or synchronized block receives the lock; all other threads that wish to utilize the shared resources must wait for the first thread to complete and the lock to be released.
In the event of many objects, two distinct threads will acquire the locks and enter a synchronized block or synchronize in java procedure with a separate lock for each object at the same time. We will utilize static synchronization to avoid this.
Synchronize in java keywords will be placed before the static method in this case.
Syntax:
synchronized static return_type method_name (Parameters) {
//code
}
Or
synchronized static return_type method_name (Class_name.class) {
//code
}
Program without Static Synchronization:
class Power{
synchronized void printPower(int n){ //static synchronized method
int temp = 1;
for(int i=1;i<=5;i++){
System.out.println(Thread.currentThread().getName() + “:- ” +n + “^”+ i + ” value: ” + n*temp);
temp = n*temp;
try{
Thread.sleep(400);
}catch(Exception e){}
}
}
}
class Thread1 extends Thread{
Power p;
Thread1(Power p){
this.p=p;
}
public void run(){
p.printPower(2);
}
}
class Thread2 extends Thread{
Power p;
Thread2(Power p){
this.p=p;
}
public void run(){
p.printPower(3);
}
}
class Thread3 extends Thread{
Power p;
Thread3(Power p){
this.p=p;
}
public void run(){
p.printPower(5);
}
}
class Thread4 extends Thread{
Power p;
Thread4(Power p){
this.p=p;
}
public void run(){
p.printPower(8);
}
}
public class Synchronization_Example4{
public static void main(String args[]){
Power ob1 = new Power(); //first object
Power ob2 = new Power(); //second object
Thread1 p1 = new Thread1(ob1);
Thread2 p2 = new Thread2(ob1);
Thread3 p3 = new Thread3(ob2);
Thread4 p4 = new Thread4(ob2);
p1.start();
p2.start();
p3.start();
p4.start();
}
}
Output:
Thread-2:- 5^1 value: 5
Thread-0:- 2^1 value: 2
Thread-2:- 5^2 value: 25
Thread-0:- 2^2 value: 4
Thread-2:- 5^3 value: 125
Thread-0:- 2^3 value: 8
Thread-2:- 5^4 value: 625
Thread-0:- 2^4 value: 16
Thread-2: – 5^5 value: 3125
Thread-0: – 2^5 value: 32
Thread-3:- 8^1 value: 8
Thread-1:- 3^1 value: 3
Thread-3:- 8^2 value: 64
Thread-1:- 3^2 value: 9
Thread-3:- 8^3 value: 512
Thread-1:- 3^3 value: 27
Thread-3:- 8^4 value: 4096
Thread-1:- 3^4 value: 81
Thread-3:- 8^5 value: 32768
Thread-1:- 3^5 value: 243
If you carefully look at the following findings, you’ll see that Thread-0, Thread-1, and Thread-2 all belong to Object-1, whereas Thread-3, Thread-4, and Thread-5 all belong to Object-2. As a result, there is no interference between threads 0 and 1 due to the same object (obj1). Similarly, there is no conflict between Threads 2 and 3 because they are part of the same object (obj2). However, there is crosstalk between Threads 0 and 2, as well as interference between Threads 1 and 3. We employ static synchronize in java to solve this problem.
Program with static synchronization:
class Power{
synchronized static void printPower(int n){ //static synchronized method
int temp = 1;
for(int i=1;i<=5;i++){
System.out.println(Thread.currentThread().getName() + “:- ” +n + “^”+ i + ” value: ” + n*temp);
temp = n*temp;
try{
Thread.sleep(400);
}catch(Exception e){}
}
}
}
class Thread1 extends Thread{
Power p;
Thread1(Power p){
this.p=p;
}
public void run(){
p.printPower(2);
}
}
class Thread2 extends Thread{
Power p;
Thread2(Power p){
this.p=p;
}
public void run(){
p.printPower(3);
}
}
class Thread3 extends Thread{
Power p;
Thread3(Power p){
this.p=p;
}
public void run(){
p.printPower(5);
}
}
class Thread4 extends Thread{
Power p;
Thread4(Power p){
this.p=p;
}
public void run(){
p.printPower(8);
}
}
public class Synchronization_Example4{
public static void main(String args[]){
Power ob1 = new Power(); //first object
Power ob2 = new Power(); //second object
Thread1 p1 = new Thread1(ob1);
Thread2 p2 = new Thread2(ob1);
Thread3 p3 = new Thread3(ob2);
Thread4 p4 = new Thread4(ob2);
p1.start();
p2.start();
p3.start();
p4.start();
}
}
Output:
Thread-0:- 2^1 value: 2
Thread-0:- 2^2 value: 4
Thread-0:- 2^3 value: 8
Thread-0:- 2^4 value: 16
Thread-0:- 2^5 value: 32
Thread-1:- 3^1 value: 3
Thread-1:- 3^2 value: 9
Thread-1:- 3^3 value: 27
Thread-1:- 3^4 value: 81
Thread-1:- 3^5 value: 243
Thread-2:- 5^1 value: 5
Thread-2:- 5^2 value: 25
Thread-2:- 5^3 value: 125
Thread-2:- 5^4 value: 625
Thread-2:- 5^5 value: 3125
Thread-3:- 8^1 value: 8
Thread-3:- 8^2 value: 64
Thread-3:- 8^3 value: 512
Thread-3:- 8^4 value: 4096
Thread-3:- 8^5 value: 32768
We can see in this static synchronize in java that there is no conflict between Thread-0 and Thread-2, as well as no conflict between Thread-1 and Thread-3. The following thread executes only once the preceding thread has completed or released the lock.
Inter–Thread Communication
Inter–thread communication or collaboration is the exchange of information between two or more threads. It is possible to do so using the techniques listed below.
- wait()
- notify()
- notifyAll()
Why do we require inter-thread communication?
- There is a circumstance on the thread where some conditions are checked continuously, and once that condition is satisfied, the thread proceeds with the appropriate action. This is referred to as polling. This is a waste of CPU time; to prevent CPU time waste due to polling, Java employs the Inter–Thread Communication Mechanism.
- wait(), notify(), and notifyAll() methods must call within a synchronize in java method or block; otherwise, the application will compile but throw an illegal Monitor State Exception when run.
Example:
class Power{
void printPower(int n){
int temp = 1;
for(int i=1;i<=5;i++){
System.out.println(Thread.currentThread().getName() + “:- ” +n + “^”+ i + ” value: ” + n*temp);
temp = n*temp;
try{
this.wait(); //wait placed outside of the synchronized block or method
Thread.sleep(500);
}catch(Exception e){System.out.println(e);}
}
}
}
Output:
Thread-0:- 5^1 value: 5
java.lang.IllegalMonitorStateException
Thread-0:- 5^2 value: 25
java.lang.IllegalMonitorStateException
Thread-0:- 5^3 value: 125
java.lang.IllegalMonitorStateException
Thread-0:- 5^4 value: 625
java.lang.IllegalMonitorStateException
Thread-0:- 5^5 value: 3125
java.lang.IllegalMonitorStateException
Thread-1:- 8^1 value: 8
java.lang.IllegalMonitorStateException
Thread-1:- 8^2 value: 64
java.lang.IllegalMonitorStateException
Thread-1:- 8^3 value: 512
java.lang.IllegalMonitorStateException
Thread-1:- 8^4 value: 4096
java.lang.IllegalMonitorStateException
Thread-1:- 8^5 value: 32768
java.lang.IllegalMonitorStateException
-
wait () Method
It forces the current thread to enter the waiting stage till another thread calls the notify() or notifyAll() methods on this object.
-
notify () Method
This function starts a single thread on the same object named wait (). If there are many threads waiting on the same object, any one of them can be picked at random to be woken. The awakened thread will be unable to proceed until the current thread release lock is released. If any other threads are attempting to obtain the lock on this object, the awakened thread will compete with them in the normal manner.
Syntax:
public final void notify()
-
notify All() Method
Rather than calling up a specific thread, it wakes up all threads that are waiting on this object monitor. The awakened thread will be unable to proceed until the lock is freed by the current thread. Once again, these awakened threads must compete with all other threads vying for the lock on this object synchronize in java.
Syntax:
public final void notifyAll()
The Need for Synchronize in Java
We utilize the keyword synchronize in Java to aid in the execution of many concurrent programming operations. The following are some of the important characteristics of the synchronized keyword:
- The synchronize in Java keyword allows for locking, which assures that no race situation occurs between threads.
- The synchronization in the java keyword also prevents the program statements from being reordered.
- Locking and unlocking are provided via the synchronized keyword. Before entering the synchronized block, the thread must obtain the lock. It reads data from the main memory after obtaining the lock.
It discharges the write operation after reading the data and then releases the lock.
Significance of the synchronized keyword in Java
- Synchronize in Java, the synchronized keyword ensures that only one thread can access shared data at a time.
- Using the Java synchronized keyword, we can only synchronize in java a block or a method.
- When a thread enters a synchronized block, it obtains a lock. And, when the thread exits that method, it releases the lock.
- A NullPointerException may be thrown if we try to utilize a null object in the synchronized block.
- We cannot utilize more than one JVM to offer access control to a shared resource when using the Java synchronized keyword.
- The system’s performance may suffer as a result of the synchronization in the java keyword’s slow operation.
- We should utilize the Java synchronized block instead of the synchronize in java method.
- If we do not correctly integrate synchronization in our code, we may have deadlock or starvation.
- Synchronize in Java, it is illegal to use a synchronized keyword with the function Object() { [native code] }. In addition, the synchronized keyword cannot be used with variables in Java.
- Wait(), notify(), and notifyAll are three significant methods offered in the Object class that we may utilize while developing synchronize in Java ().
The Drawback of Synchronization Mechanism
The Synchronization Mechanism underperforms.
Consider the following scenario: If there are five processes P1, P2, P3, P4, and P5 that are waiting for shared resources to access only one thread at a time, and all other processes are in a waiting state, the final process must wait until all other processes are finished. As a result, we must employ the synchronize in java idea, which yields errors.
Conclusion
Synchronize in Java, synchronization is the ability to regulate multiple processes’ access to a shared resource. Multiple threads attempt to access shared resources at the same time under the Multithreading concept, resulting in inconsistent outcomes. Synchronization is required for thread-to-thread communication to be reliable. Synchronization aids in thread interference prevention.
In this Java blog, we covered various methods for achieving synchronization by leveraging the synchronized keyword. It may be used with methods or within the block of a technique. We investigate the requirement in synchronize in Java. Finally, we went through each method of utilizing a synchronized keyword with an example to assist you to understand.
Frequently Asked Question’s
1. What is synchronize in Java?
Java is a prominent computer language that was developed in 1995. Oracle owns it, and it is used by over 3 billion devices. Synchronize In Java, is the ability to regulate multiple threads’ access to a shared resource. Multiple threads attempt to access shared resources at the same time under the Multithreading concept, resulting in inconsistent outcomes. Synchronize in java is required for thread-to-thread communication to be reliable.
2. What are the types of synchronization?
There are two forms of synchronization.
- Process Synchronization
- Thread Synchronization
Process Synchronize in java
A process is nothing more than a programme in execution. It operates in a separate process that is not connected to another. The operating system allocates resources to the process, such as memory and CPU time.
The phrase “process synchronization” refers to the sharing of capabilities between two or more processes while guaranteeing data consistency. The Critical Section is a piece of code that is shared by several processes in a programming language. There are various methods to prevent critical section problems, such as Peterson’s Solution, but the most famous is Semaphores.
Thread Synchronize in java
Thread Synchronize in java refers to the concurrent execution of a vital resource by two or more Threads. A thread is a subroutine that can run separately within the context of a single process.
A single process can have numerous threads, and the program can schedule all of the threads to use a vital resource. A single thread, in reality, includes numerous threads.
3. Which statement is true about synchronization in Java programming?
Multiple threads can access any object of a class using the synchronize in java function. The synchronized method restricts access to a class’s objects to a single thread. Answer: The synchronized method restricts access to distinct objects of a class to a single thread.
4. What is non synchronization in Java?
Non-synchronized implies that at any given time, two or more threads can access the methods of that particular class. A non-synchronized class would be StringBuilder. A non-synchronized class is not thread-safe in general. (However, certain non-synchronized classes are thread-safe.)
5. How synchronization is implemented in Java?
The synchronization accomplishes synchronize in Java through the use of a notion known as monitors. One thread can only own a monitor at a time. A thread is considered to have entered the monitor when it obtains a lock. All subsequent threads attempting to enter the locked monitor will be halted until the initial thread departs.
6. Can static methods be synchronized?
A static synchronized method is a means of synchronizing a method synchronize in Java so that no two threads can perform on the synchronized method at the same time. The only difference is that Static Synchronized is used. We are achieving a class-level lock, which will allow just one thread to act on the function.
7. What is difference between lock and synchronization in Java
The primary distinction between lock and synchronize in java is that with locks, you may release and acquire the locks in any sequence. With synchronized, you may only release locks in the order they were obtained.
8. Why is synchronization needed?
The primary goal synchronize in java is to prevent thread interference. When several threads attempt to access a shared resource, we must guarantee that the resource is only accessed by one thread at a time. Synchronization is the mechanism through which this is accomplished.
9. Can two threads access the same object?
You must exercise extreme caution here since two threads can access two separate synchronized methods if one is static and the other is not. Data inconsistency problems might occur if both techniques update the same data. The class object is utilized as the object reference in this scenario.
10. Can constructor be synchronized in Java?
It is important to note that constructors cannot be synchronize in java; using the synchronized keyword with a function Object() { [native code] } is a syntactic mistake. It makes no sense to synchronize in java constructors since only the thread that generates an object should have access to it while it is being built.
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