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1.1.3. Thread Life Cycle
Interactive Audio Lesson
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Today, we will discuss the thread life cycle in Java. Can anyone tell me what they think happens when a thread is created?
I think it goes into a kind of waiting state until it gets started.
Great observation! When a thread is created, it is in the 'New' state. This means it has been instantiated but not started yet. Now, what happens once we initiate it?
It becomes Runnable, right?
Exactly! The thread moves to the 'Runnable' state where it waits for CPU availability. It’s important to remember that 'Runnable' means it is ready to run, but not necessarily running yet. Let's remember this with the acronym 'NRR' for New, Runnable, Running.
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Now, let's delve deeper. What does it mean when a thread is in the 'Running' state?
It means the thread is currently executing its task.
Correct! The 'Running' state indicates that the thread is performing its task actively. But what can cause a thread to enter the 'Blocked/Waiting' state?
It happens when it's waiting for a monitor lock, like when other threads are holding resources.
That's a perfect explanation! We can recall this concept with the phrase 'Locking leads to Blocking.' Remember to always check if resources are available before a thread tries to execute.
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Create a free accountFinally, let's talk about the 'Terminated' state. Can anyone tell me what might cause a thread to reach this status?
It could finish its task or be stopped by another thread.
Exactly! Once a thread finishes executing its run method, it transitions to the 'Terminated' state. To remember the states more easily, think of the phrase 'Born, Ready, Busy, Waiting, Goodbye.'
Overview
Short Summary
The thread life cycle in Java describes the various states a thread can be in during its execution.
Medium Summary
In the thread life cycle, a Java thread can exist in one of five states: New, Runnable, Running, Blocked/Waiting, and Terminated. Understanding these states is crucial for managing thread behavior effectively in a multi-threaded application.
Detailed Summary
Thread Life Cycle
In Java, a thread can exist in one of the following states, illustrating its status during execution:
- New: When a thread is created but not yet started. It is essentially an object of the
Threadclass that has not begun its activity. - Runnable: The thread is eligible to run and is waiting for CPU availability. This means the thread can be in a state of execution but isn't guaranteed to be actively running.
- Running: The thread is actively executing its task.
- Blocked/Waiting: Indicates that the thread is not able to proceed because it is waiting for a monitor lock (to enter a synchronized block or method) or is waiting for a signal (like
wait()) from another thread. - Terminated: The thread has completed its execution, either by finishing its work or by being stopped forcibly.
Understanding these states is essential for managing thread behavior effectively, as it impacts synchronization and resource accessibility in concurrent applications.
Reference YouTube Videos
Audio Book
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Create a free accountA thread in Java can be in one of the following states:
- New – Created but not yet started.
- Runnable – Eligible to run, waiting for CPU.
- Running – Actively executing.
- Blocked/Waiting – Waiting for a monitor lock or a signal.
- Terminated – Execution completed or stopped.
Detailed Explanation
In Java, a thread can exist in five different states throughout its life cycle.
- New: This is the initial state when a thread is created but hasn't started executing yet. It is only in memory, and its method
start()needs to be called to transition it. - Runnable: Once the thread is eligible to run but is waiting for the CPU, it is in this state. It can transition to the Running state when the CPU scheduler allocates CPU time to it.
- Running: This is the state where the thread is actively executing its code. This state is where the thread performs its intended functions.
- Blocked/Waiting: A thread enters this state when it is waiting for a resource (like a lock) or a signal to continue its execution. This can happen if another thread holds the resource it needs.
- Terminated: Once a thread completes its execution or is stopped, it enters the Terminated state. At this point, the thread has released all its resources.
Examples & Analogies
Think of a thread's life cycle like a worker in an office.
- The 'New' state is similar to when a new employee joins the company but hasn’t started working yet.
- In the 'Runnable' state, the worker is ready and waiting for their turn to work on a project, just like waiting in a line.
- The 'Running' state is when the employee is actively working on their tasks and completing them.
- In the 'Blocked/Waiting' state, the worker might be waiting for a colleague to provide them with information or resources to complete their work. Finally, when they finish all tasks or leave the company, they enter the 'Terminated' state.
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Key Concepts
Core takeaways and short definitions to help you quickly recall the key ideas from this section.
New: Indicates the initial state of a thread.
Runnable: Ready to run but not yet executing.
Running: Actively executing the thread’s task.
Blocked/Waiting: Inability to proceed due to waiting for locks or signals.
Terminated: Indicates thread completion.
Examples
Step-by-step examples to apply the section's ideas and test your understanding.
A newly created thread is in the 'New' state until the start method is called.
A thread becomes 'Runnable' when it is eligible for CPU time after starting.
Once a thread's run method completes, it transitions to the 'Terminated' state.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
Stories
Flash Cards
Glossary
New
State of a thread that has been created but not yet started.
Runnable
State of a thread that is ready to run and waiting for CPU time.
Running
State of a thread that is currently executing its task.
Blocked/Waiting
State of a thread that is unable to proceed until it acquires a monitor lock or receives a signal.
Terminated
State of a thread that has completed its execution.