java reflection interview questions and answers

#JAVA REFLECTION INTERVIEW QUESTIONS AND ANSWERS PC#

Each Thread class has a field called threadLocals of type ThreadLocal.ThreadLocalMap. It allows developer to store variables pertaining to a particular thread so that multiple threads do not need to access shared variables, causing hazard to data consistency. What is the use of ThreadLocal? ThreadLocal is a mechanism to ensure thread safety. Moreover, synchronized is implemented based on operating system which causes the thread to fall into the kernel mode instead of user mode which is a time-consuming process.Ĩ. In contrast, volatile allows concurrent executions from multiple threads by forcing them to read the variable from main memory directly instead of CPU cache. This causes concurrency issue as threads on the same object protected by synchronization can’t execute concurrently. After synchronized block is writing/modifying the resource, the variable value is flushed back to the shared memory space. What are the differences between volatile and synchronized? Volatile is a lightweight lock whereas synchronized is a heavyweight lock.

When one thread is manipulating the resources, other threads who want to access the same object are not allowed to execute.ħ. It allows only one thread to access the resources at a given point of time. Synchronized keyword is used for a block of code. This is done by forcing the variable to be accessed through main memory instead of cache memory. What are volatile and synchronized keywords? Volatile keyword targets at a field, or a variable in a method, such that when multiple threads access the same variable, data consistency is ensured. Using Condition.await() and Condition.signal() methods, we can put a thread to sleep or wake up a thread to do its work.Ħ.

Once a certain condition fulfills, another thread will call the notify() method to wake up the first thread, and let it enter a runnable state.ģ) Lock/Condition mechanism Lock is class provided by Java to limit access to an object. wait() method makes object convert from running state to blocking state. What are the communication methods between threads in Java? 1) Shared memory volatile keyword, synchronized keywordĢ) wait and notify mechanism wait() and notify() are the methods of Java Object. So native method stack is not shared across multiple threads.ĥ. Native method stack is similar to stack area which also contains local variables and methods.

#JAVA REFLECTION INTERVIEW QUESTIONS AND ANSWERS PC#

PC register tracks the command on how the thread should progress so it is independent for each thread as well. The stack area which stores the methods, local variables within a thread is not shared as each thread has different methods of calling and variables. Therefore, heap area is also a shared space. Heap area stores global variables, object instances, and things that could be accessed anywhere within the application. In JVM Runtime Data Area, what are the components that are shared between multiple threads? Method area is shared among threads.

Java reflection interview questions and answers