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Different States of a Thread:

Different states of a Thread: 

Threads are in a new state when they are created. In this state, the code has yet to be executed.

Runnable State: 

A Thread is moved to a Runnable State when it is ready to execute. In this state, a Thread might be running, or it might be prepared to run whenever there is a place to, organized by the Thread Scheduler.

In a Multi-Thread process, a specific amount of time is allocated to each Thread. Each Thread gets a specific allocated timeframe to run before switching to a new Thread, giving each equal opportunity to execute the actions. When this happens, all Threads running, waiting to run, or waiting for the CPU, lie in a Runnable State.

Blocked/Waiting state:

When a Thread is inactive for a brief time, it is said to be in one of these states:

  • Blocked
  • Waiting

The Thread Scheduler is responsible for reactivating and scheduling the blocked/waiting Thread back to a Runnable State. A Thread will not be able to continue until it has been moved back to the Runnable State. Whilst in a Blocked/Waiting state, there is no CPU cycle being consumed.


If a Thread is trying to access a part of code currently being blocked by another Thread, it is in the Blocked state. Only when the protected area is unlocked will the Scheduler pick the Thread and move it into the Runnable State. 


A Thread is in a Waiting state when there is a condition that is currently preventing the code from being run. Once the condition is fulfilled, the Thread will be sent to the Runnable state by the Thread Scheduler to continue.


If a Thread is moved to the Blocked/Waiting state, another Thread will be transferred to the Runnable state to run while the condition is fulfilled or granted access. This decision making is all controlled by the Thread Scheduler. 

Timed Waiting: 

A thread lies in a Timed Waiting state when a timeout parameter is called. A Thread will remain in this state until the timeout has finished or a notification has been received. For example, when a thread calls sleep, it is moved to the Timed Waiting state.

Terminated State: 

There are a few reasons that can lead to the Thread Terminating :

  • Because the Termination should exist. This happens when the program completes the code.
  • Because there was an error whilst running the code in the Thread.

A thread that lies in a terminated state does no longer consumes any cycles of CPU.

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