Is thread can acquire multiple lock simultaneously?

Ans) Yes. A thread can hold multiple locks at the same time. Once a thread acquires a lock and enters into the synchronized method / block, it may call another synchronized method and acquire a lock on another object.

People also ask, can multiple thread exist on one object?

As multiple threads exists on same object. Only one thread can hold object monitor at a time. As a result thread can notify other threads of same object that lock is available now.

Also, what will happen if two threads of the different priority value are called to run simultaneously? If two threads of the same priority are waiting for the CPU, the scheduler chooses one of them to run in a round-robin fashion. The chosen thread will run until one of the following conditions is true: A higher priority thread becomes runnable. It yields, or its run method exits.

Accordingly, can two threads access a synchronized method at the same time?

Yes and no: Yes, if the method is called on different instances of the class. No, two threads can't simultaneously call synchronized methods on the same instance of the class. This is the case even if the two threads call different methods (as long as the instance is the same).

Can you start a thread twice?

No. After starting a thread, it can never be started again. If you does so, an IllegalThreadStateException is thrown. In such case, thread will run once but for second time, it will throw exception.

What is a daemon thread?

Daemon thread is a low priority thread (in context of JVM) that runs in background to perform tasks such as garbage collection (gc) etc., they do not prevent the JVM from exiting (even if the daemon thread itself is running) when all the user threads (non-daemon threads) finish their execution.

What is difference between user thread and daemon thread?

The main difference between a user thread and a daemon thread is that your Java program will not finish execution until one of the user thread is live. On the other hand, a daemon thread doesn't get that preference, JVM will exit and close the Java program even if there is a daemon thread running in the background.

Which state is entered once a thread is created?

runnable state

Why sleep () is static method?

sleep() method is used to pause the execution, relinquish the CPU and return it to thread scheduler. sleep() will put Thread "t" into sleeping state, that's not true because Thread. sleep method is a static method it always put the current thread into Sleeping state and not thread "t".

How many prior values a thread can be assigned?

Accepted value of priority for a thread is in range of 1 to 10. There are 3 static variables defined in Thread class for priority. public static int MIN_PRIORITY: This is minimum priority that a thread can have. Value for this is 1.

How can two threads communicate with each other?

Inter-thread Communication All the threads in the same program share the same memory space. If an object is accessible to various threads then these threads share access to that object's data member and thus communicate each other. The second way for threads to communicate is by using thread control methods.

What is object lock and when a thread required?

Object level lock in Java Object level lock is mechanism when we want to synchronize a non-static method or non-static code block such that only one thread will be able to execute the code block on given instance of the class. This should always be done to make instance level data thread safe.

How can we avoid deadlock in Java?

How To Avoid Deadlock in Java?

1. Avoid Nested Locks – You must avoid giving locks to multiple threads, this is the main reason for a deadlock condition.
2. Avoid Unnecessary Locks – The locks should be given to the important threads.

What happens if you try to start a thread that's already been started?

If you try starting a thread which has been already started once an IllegalThreadStateException is thrown, which is a runtime exception. A thread in runnable state or a dead thread can not be restarted.

What is an advantage of using the runnable interface?

Java only supports single inheritance, so you can only extend one class. Instantiating an interface gives a cleaner separation between your code and the implementation of threads. Implementing Runnable makes your class more flexible. If you extend Thread then the action you're doing is always going to be in a thread.

What is the use of synchronization?

The Java synchronized keyword is an essential tool in concurrent programming in Java. Its overall purpose is to only allow one thread at a time into a particular section of code thus allowing us to protect, for example, variables or data from being corrupted by simultaneous modifications from different threads.

What happens when a thread Cannot acquire a lock on an object?

What happens when a thread cannot acquire a lock on an object. If a thread attempts to execute a synchronized method or synchronized statement and isunable to acquire an object's lock, it enters the waiting state until the lock becomesavailable.

Which method can be used to find that thread holds lock?

Or, you can use a commercial profiler like YourKit or any number of other profilers. You can check the lock on the particular object by calling wait() or notify() method on that object. If the object does not hold the lock, then it will throw llegalMonitorStateException . 2- By calling holdsLock(Object o) method.

Can two synchronized methods in same class?

Yes, they can run simultaneously both threads. If you create 2 objects of the class as each object contains only one lock and every synchronized method requires lock. So if you want to run simultaneously, create two objects and then try to run by using of those object reference.

What happens when a thread executes wait () method on an object without owning the object's lock?

The wait(), notify(), and notifyAll() methods should be called for an object only when the current thread has already locked the object's lock. Note also that wait() forces the thread to release its lock. This means that it must own the lock of an object before calling the wait() method of that (same) object.

How many locks does an object have in Java?

17.1 Locks

What is class level synchronization in Java?

Class level locking: Class level locking means you want to synchronize static method or block so that it can be accessed by only one thread for whole class. If you have 10 instances of class, only one thread will be able to access only one method or block of any one instance at a time.