Life cycle of thread

Life cycle of thread in java

• Its recommended to learn about life cycle of Thread before you start programming on Thread.
• Threads exists in different type of states.
   

• Thread having below states.

1. New State
2. Ready State
3. Running State
4. Dead State
5. Non Runnable States 

Life cycle of thread in java with diagram 

1.New State:

• A thread has been created but not started yet. A thread will be started by calling its start() method.

2.Runnable State:

• This state is also called ready to run stage also called queue. A thread starts in runnable state by calling start() method.
• The Thread scheduler decides which thread runs and how long.

3.Running State:

• If a Thread is executing that means Thread is in Running stage.

4.Dead State:

• Once a Thread reached dead state it can not run again.

5. Non runnable States:

• A Running Thread transit to one of the non runnable states, depending upon the circumstances.
• A Thread remains non runnable until a special transition occurs.
• A Thread does not go directly to the running state from non runnable state.
• But transits first to runnable state.

1. Sleeping: The Threas sleeps for specified amount of time.
2. Blocked for I/O: The Thread waits for a blocking operation to complete.
3. Blocked for join completion: The Thread waits for completion of another Thread.
4. Waiting for notification: The Thread waits for notification another Thread.
5. Blocked for lock acquisition: The Thread waits to acquire the lock of an object.

• JVM executes the Thread based on their priority and scheduling.

Thread Scheduler:

• Schedulers in JVM implementations usually employ one of these two Strategies.
• Preemptive Scheduling
• Time Sliced or Round robin Scheduling

• Thread schedulers are implementation and platform independent, therefore how thread will scheduled is unpredictable

Thread priority:

• JVM will assign a priority for every Thread created in it.
• 0- will be the minimum priority
• 5- will be the normal priority
• 10- will be the maximum priority

• To hold all these values Thread class has below three corresponding variables
• public static final int MIN_PRIORITY
• public static final int NORM_PRIORITY
• public static final int MAX_PRIORITY 

•  A thread inherits the priority of its parent Thread. The default priority of the every thread is normal priority 5, because main thread priority is 5.
• We can set the priority of a thread by using setPriority(int priority) method
• public final void setPriority(int priority)
• public void getPriority();
• User defined thread created with default name  Thread+<index>, where index is the integer number starts from 0.
• The name of a thread can be change using setName(String name) method.
• Get by using getName() method.
• public final void setName(String name)
• public final String getName().