thread life cycle in java
In Java, a thread goes through several states during its lifetime, which are defined by the Thread.State
enumeration. The states are:
- NEW: The thread has been created but has not yet started.
- RUNNABLE: The thread is running, or is ready to run if a processor is available.
- BLOCKED: The thread is waiting for a monitor lock to be released.
- WAITING: The thread is waiting indefinitely for another thread to perform a particular action.
- TIMED_WAITING: The thread is waiting for a specified period of time for another thread to perform a particular action.
- TERMINATED: The thread has completed execution and has exited.
Here is an overview of the typical lifecycle of a thread in Java:
Creating the Thread: A new thread is created by instantiating an object of the
Thread
class, and then invoking thestart()
method to initiate the thread.Runnable: The thread enters the
Runnable
state after thestart()
method is invoked. The thread is considered to be in this state until it is selected to run by the thread scheduler.Running: When the thread is selected to run by the thread scheduler, it enters the
Running
state. This is where the thread actually performs its intended task.Blocked/Waiting/Timed_Waiting: If a running thread performs a blocking operation, such as waiting for I/O or acquiring a lock on an object, it enters the
Blocked
state. If it waits for another thread to perform a particular action, it enters theWaiting
state. If it waits for a specified period of time, it enters theTimed_Waiting
state.Terminated: When the
run()
method completes or when the thread is interrupted or stopped, the thread enters theTerminated
state.
It's worth noting that the transition between states is not always deterministic and can be affected by factors such as the underlying hardware and the operating system. Also, the Java Virtual Machine (JVM) manages the thread lifecycle, so the programmer does not have direct control over the states of a thread.