Why is synchronized block better than ConcurrentHashMap?

ConcurrentHashMap allows performing concurrent read and write operation. Hence, performance is relatively better than the Synchronized Map. In Synchronized HashMap, multiple threads can not access the map concurrently. Hence, the performance is relatively less than the ConcurrentHashMap.

Why synchronized block is better than synchronized method?

synchronized block has better performance as only the critical section is locked but synchronized method has poor performance than block. synchronized block provide granular control over lock but synchronized method lock either on current object represented by this or class level lock.

Should I use synchronized with ConcurrentHashMap?

You should use ConcurrentHashMap when you need very high concurrency in your project. It is thread safe without synchronizing the whole map . Reads can happen very fast while write is done with a lock.

Why might you use a synchronized block?

A Synchronized block is a piece of code that can be used to perform synchronization on any specific resource of the method. A Synchronized block is used to lock an object for any shared resource and the scope of a synchronized block is smaller than the synchronized method.

Is synchronized method more efficient?

If you synchronize a code block within that method then more than one thread can execute the method simultaneously, but only one thread can enter the synchronized block at a time. From this we can conclude that synchronizing on the smallest possible code block required is the most efficient way to do it.

#12 - Difference b/w ConcurrentHashMap

What is the advantage of a synchronized block over a mutex?

The main difference is that if you use a synchronized block you may lock on an object other than this which allows to be much more flexible.

Why do we need synchronized block in Java?

Synchronized block is used to lock an object for any shared resource. Scope of synchronized block is smaller than the method. A Java synchronized block doesn't allow more than one JVM, to provide access control to a shared resource.

Why do we need synchronization?

We need to synchronize the shared resources to ensure that at a time only one thread is able to access the shared resource. If an Object is shared by multiple threads then there is need of synchronization in order to avoid the Object's state to be getting corrupted. Synchronization is needed when Object is mutable.

Does synchronized method lock whole class?

It's possible that both static synchronized and non static synchronized method can run simultaneously or concurrently because they lock on different object. If a thread takes monitor on static synchronized method, it takes the lock on the Class level itself.

Which is better to use synchronized over the map or using ConcurrentHashMap?

ConcurrentHashMap allows performing concurrent read and write operation. Hence, performance is relatively better than the Synchronized Map. In Synchronized HashMap, multiple threads can not access the map concurrently. Hence, the performance is relatively less than the ConcurrentHashMap.

What is the difference between ConcurrentHashMap and Synchronised HashMap?

synchronizedMap() requires each thread to acquire a lock on the entire object for both read/write operations. By comparison, the ConcurrentHashMap allows threads to acquire locks on separate segments of the collection, and make modifications at the same time.

Is ConcurrentHashMap slower than HashMap?

Only modifying operations on ConcurrentHashMap are synchronized. Hence, add or remove operations on ConcurrentHashMap are slower than on HashMap . The read operations on both, ConcurrentHashMap and HashMap , give same performance as read operations on both maps are not synchronized.

What is Singleton is it better to make whole method synchronized or only critical section synchronized?

Since synchronization is only needed during initialization on singleton instance, to prevent creating another instance of Singleton, It's better to only synchronize critical section and not whole method.

What is thread starvation in Java?

Starvation describes a situation where a thread is unable to gain regular access to shared resources and is unable to make progress. This happens when shared resources are made unavailable for long periods by "greedy" threads.

Can we use static and synchronized together?

static methods can be synchronized. But you have one lock per class. when the java class is loaded coresponding java.

What is the disadvantage of synchronization?

The main advantage of synchronization is that by using the synchronized keyword we can resolve the date inconsistency problem. But the main disadvantage of a synchronized keyword is it increases the waiting time of the thread and affects the performance of the system.

What is the use of synchronized method in Java?

Java Synchronized Method

Synchronized method is used to lock an object for any shared resource. When a thread invokes a synchronized method, it automatically acquires the lock for that object and releases it when the thread completes its task.

Why do we need synchronization in distributed systems?

Each node in distributed systems can share their resources with other nodes. So, there is need of proper allocation of resources to preserve the state of resources and help coordinate between the several processes. To resolve such conflicts, synchronization is used.

Why is synchronization necessary explain with the help of a relevant example?

Synchronization control the access the multiple threads to a shared resources. Without synchronization of threads, one thread can modify a shared variable while another thread can update the same shared variable, which leads to significant errors.

How many threads per instance can execute inside a synchronized instance method?

Only one thread per instance can execute inside a synchronized instance method.

How can we avoid deadlock in Java?

Is HashMap synchronized?

HashMap is similar to HashTable in java. The main difference between HashTable and HashMap is that HashTable is synchronized but HashMap is not synchronized.

Can CyclicBarrier and CountDownLatch in Java be reused?

CountDownLatch cannot be reused, when count arrives at zero it can't be reset. CyclicBarrier can be reused after holding threads are released.

Why sleep and yield methods are static?

The code would only execute when someXThread was executing, in which case telling someYThread to yield would be pointless. So since the only thread worth calling yield on is the current thread, they make the method static so you won't waste time trying to call yield on some other thread.