{"id":983,"date":"2025-06-11T10:54:27","date_gmt":"2025-06-11T07:54:27","guid":{"rendered":"https:\/\/www.certbolt.com\/certification\/?p=983"},"modified":"2025-12-30T14:48:04","modified_gmt":"2025-12-30T11:48:04","slug":"java-thread-basics-and-execution-life-cycle","status":"publish","type":"post","link":"https:\/\/www.certbolt.com\/certification\/java-thread-basics-and-execution-life-cycle\/","title":{"rendered":"Java Thread Basics and Execution Life Cycle"},"content":{"rendered":"

A thread in Java is the smallest unit of execution within a program. Every Java application starts with a single thread, known as the main thread, which is initiated by the Java Virtual Machine (JVM) at the start of program execution. The main thread begins by invoking the main() method, from which the program’s operations commence.<\/span><\/p>\n

In Java, a thread represents a separate path of execution. Java programs can utilize multiple threads to execute tasks concurrently, allowing for more efficient use of system resources. Each thread can operate independently while sharing the same memory space, which facilitates efficient communication and data sharing between threads. Threads are scheduled based on priority, and higher-priority threads are generally executed before lower-priority ones.<\/span><\/p>\n

Threads in Java are essential for managing multiple tasks within the same program, such as performing computations while maintaining a responsive user interface or handling multiple client requests in server-side applications. Each thread maintains its own program counter, stack, and local variables, which enables it to execute independently of other threads.<\/span><\/p>\n

Java threads enable concurrent execution, which is particularly beneficial for tasks like input\/output operations, network communications, and other time-consuming processes. Understanding how to create and manage threads effectively is crucial for building responsive and efficient Java applications.<\/span><\/p>\n

Creating a Thread in Java<\/b><\/p>\n

Extending the Thread Class<\/b><\/p>\n

One way to create a thread in Java is by extending the <\/span>java.lang.Thread<\/span> class. This involves defining a new class that inherits from Thread and overriding the <\/span>run()<\/span> method to specify the actions the thread should perform.<\/span><\/p>\n

Example:<\/span><\/p>\n

class MyThread extends Thread {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0public void run() {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0System.out.println(«Thread is running»);<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0}<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0public static void main(String[] args) {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0MyThread t1 = new MyThread();<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0t1.start();<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0}<\/span><\/p>\n

}<\/span><\/p>\n

In this example, the <\/span>start()<\/span> method is used to create and launch a new thread, which then executes the code defined in the <\/span>run()<\/span> method.<\/span><\/p>\n

Implementing the Runnable Interface<\/b><\/p>\n

Another way to create a thread in Java is by implementing the <\/span>Runnable<\/span> interface. This approach involves creating a class that implements <\/span>Runnable<\/span> and defining the <\/span>run()<\/span> method. This method is then passed to a <\/span>Thread<\/span> object, which starts the thread.<\/span><\/p>\n

Example:<\/span><\/p>\n

class MyRunnable implements Runnable {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0public void run() {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0System.out.println(«Thread is running using Runnable»);<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0}<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0public static void main(String[] args) {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0MyRunnable myRunnable = new MyRunnable();<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Thread t1 = new Thread(myRunnable);<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0t1.start();<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0}<\/span><\/p>\n

}<\/span><\/p>\n

Using the <\/span>Runnable<\/span> interface is considered more flexible since the class can extend another class as well, unlike extending the Thread class, which limits inheritance.<\/span><\/p>\n

Lifecycle of a Thread in Java<\/b><\/p>\n

The lifecycle of a thread in Java represents the various states a thread can be in from creation to termination. These states are managed internally by the JVM and controlled via thread methods and scheduling mechanisms.<\/span><\/p>\n

New State<\/b><\/p>\n

When a thread object is instantiated using the <\/span>Thread<\/span> class, it is said to be in the New state. At this point, the thread has been created but has not yet started executing. The <\/span>start()<\/span> method has not been called.<\/span><\/p>\n

Runnable State<\/b><\/p>\n

Once the <\/span>start()<\/span> method is invoked on a thread object, the thread enters the Runnable state. It is now ready to run and is waiting for CPU time to be allocated by the thread scheduler. The thread is in a queue, prepared to execute as soon as it gets access to the CPU.<\/span><\/p>\n

Running State<\/b><\/p>\n

A thread transitions to the Running state when it is selected by the thread scheduler from the Runnable queue. In this state, the thread is actively executing the instructions defined in its <\/span>run()<\/span> method. The thread will remain in this state until it completes its execution or is moved to a non-runnable state.<\/span><\/p>\n

Blocked (Non-Runnable) State<\/b><\/p>\n

A thread enters the Blocked or Non-Runnable state when it is alive but not eligible to run. This can happen when the thread is waiting for a monitor lock or when the <\/span>sleep()<\/span> or <\/span>wait()<\/span> methods are called. Although the thread is still active, it cannot be scheduled for execution.<\/span><\/p>\n

Dead State<\/b><\/p>\n

A thread reaches the Dead state when it finishes executing its <\/span>run<\/span> method or when it is explicitly terminated. Once a thread enters this state, it cannot be restarted.<\/span><\/p>\n

Java Thread Priorities<\/b><\/p>\n

Each thread in Java has a priority, which helps determine the order in which threads are scheduled for execution. The priority is an integer ranging from 1 (lowest) to 10 (highest), with 5 as the default priority. Threads with higher priorities are typically given preference by the scheduler.<\/span><\/p>\n

Thread priorities can be set using the following constants:<\/span><\/p>\n