A thread in Java is a lightweight subprocess that runs concurrently with other threads within the same process. Threads share the same memory and resources of the process they belong to, but they have their own execution context and can run independently of each other.
There are two ways to create a thread in Java. The first is to extend the Thread class and override its run() method. The second is to implement the Runnable interface and pass an instance of the class to the Thread constructor.
A process is a program in execution, whereas a thread is a single sequence of instructions within a process. A process has its own memory space and resources, while threads share the same memory space and resources of the process they belong to.
To start a thread in Java, you need to call the start() method on an instance of the Thread class. This will create a new thread and invoke its run() method in a separate thread of execution.
A thread pool is a collection of pre-initialized threads that can be used to execute tasks asynchronously. Instead of creating and destroying threads for each task, a thread pool can reuse existing threads to improve performance and reduce overhead.
You can synchronize threads in Java using the synchronized keyword. This allows multiple threads to access the same shared resource in a safe and coordinated manner, preventing race conditions and other concurrency issues.
Deadlock is a situation where two or more threads are blocked and waiting for each other to release a shared resource, resulting in a deadlock or a circular waiting chain. Deadlock can cause a program to hang or become unresponsive.
The wait() method is used to make a thread wait until another thread notifies it to wake up. The sleep() method is used to make a thread pause for a specified amount of time. The wait() method releases the lock on an object, while the sleep() method does not.
A daemon thread is a low-priority thread that runs in the background to perform tasks such as garbage collection or finalization. Daemon threads do not prevent a program from exiting, and they terminate automatically when all user threads have finished executing.
A race condition is a situation where two or more threads access a shared resource in an unpredictable order, leading to unexpected behavior or incorrect results. Race conditions can occur when threads do not synchronize access to shared resources properly.