In Java, a thread is a lightweight process that runs concurrently with other threads within the same process. Each thread has its own execution stack, program counter, and set of registers, allowing it to execute independent of other threads. Threads can be used to perform multiple tasks simultaneously, allowing for efficient use of resources and improved application performance. In this article, we will discuss the lifecycle and stages of a thread in Java.
Thread Lifecycle:
The lifecycle of a thread in Java can be divided into five stages:
New:
The first stage in the lifecycle of a thread is the New stage. In this stage, a thread is created but has not yet started executing. When a thread is instantiated using the “new” keyword or by extending the “Thread” class, it enters the New stage. At this point, the thread is not yet associated with any processor time or system resources.
Runnable:
The second stage in the lifecycle of a thread is the Runnable stage. In this stage, the thread is ready to execute and waiting for processor time. When the start() method is called on a thread, it enters the Runnable stage. In this stage, the thread is added to the thread scheduler’s queue and is waiting for a chance to be executed.
Running:
The third stage in the lifecycle of a thread is the Running stage. In this stage, the thread is executing its task. When a thread is selected by the thread scheduler to run, it enters the Running stage. The thread remains in this stage until it has completed its task or has been preempted by the scheduler due to a higher priority thread becoming available.
Blocked:
The fourth stage in the lifecycle of a thread is the Blocked stage. In this stage, the thread is waiting for a specific event to occur, such as I/O input or a lock on a shared resource. When a thread encounters a blocking operation, it enters the Blocked stage. In this stage, the thread is temporarily suspended and removed from the thread scheduler’s queue until the blocking condition is resolved.
Terminated:
The final stage in the lifecycle of a thread is the Terminated stage. In this stage, the thread has completed its task or has been terminated due to an error. When a thread has completed its task, it enters the Terminated stage. The thread’s resources are released, and it is no longer available for execution.
Thread States Diagram:
The following diagram illustrates the different states in the lifecycle of a thread in Java:
+----------+
| NEW |
+----------+
|
|
v
+----------+
|RUNNABLE |
+----------+
|
|
v
+----------+
| RUNNING |
+----------+
|
|
v
+----------+
| BLOCKED |
+----------+
|
|
v
+----------+
| TERMINATED|
+----------+
Conclusion:
In Java, the lifecycle of a thread consists of five stages: New, Runnable, Running, Blocked, and Terminated. Understanding the lifecycle of a thread is essential for efficient thread management, allowing developers to write multithreaded applications that take advantage of the available resources and improve application performance. By carefully managing threads, developers can ensure that their applications perform well and are responsive to user input.
