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understanding thread states thread life cycle in java

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In Java, a thread goes through several states during its lifetime, which are represented by the Thread.State enum. The states are as follows:

  1. NEW: When a thread is created but has not yet started, it is in the NEW state.
  2. RUNNABLE: When a thread is ready to run, it is in the RUNNABLE state. This means that the thread is either running or it is waiting for a turn to run.
  3. BLOCKED: When a thread is blocked on a monitor lock, it is in the BLOCKED state. This means that the thread is waiting for a lock to be released so that it can acquire the lock and continue running.
  4. WAITING: When a thread is waiting for another thread to perform a certain action, it is in the WAITING state. For example, a thread can be waiting for a message to arrive on a queue or for a certain amount of time to elapse.
  5. TIMED_WAITING: When a thread is waiting for a certain amount of time to elapse, it is in the TIMED_WAITING state. This is similar to the WAITING state, but the thread will only wait for a specific amount of time before it resumes running.
  6. TERMINATED: When a thread has finished running or has been terminated, it is in the TERMINATED state.

A thread can transition between these states as follows:

  1. A new thread starts in the NEW state.
  2. When the start() method is called on the thread, it transitions to the RUNNABLE state.
  3. When a thread waits for a lock, it transitions to the BLOCKED state.
  4. When a thread calls the wait() method, it transitions to the WAITING state.
  5. When a thread calls the sleep() method, it transitions to the TIMED_WAITING state.
  6. When the lock is released or the specified time elapses, the thread transitions back to the RUNNABLE state.
  7. When a thread completes its execution or is terminated, it transitions to the TERMINATED state.

It's important to note that thread states are not guaranteed to occur in a certain order, and the JVM's scheduler decides when and in what order threads are executed. However, understanding the different thread states and how they transition can help you write more effective multithreaded applications.