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    Understanding the Thread Lifecycle in Java: A Comprehensive Guide

    Rumman Ansari February 04, 2025 8,598 views
    Understanding the Thread Lifecycle in Java: A Comprehensive Guide

    When a thread is created, a new thread of control is added to the current process. Every process has at least one thread of control, in the program's main() routine. Each thread in the process runs simultaneously and has access to the calling process's global data. In addition, each thread has its own private attributes and call stack.

    A thread can be in one of the five states. According to sun, there is only 4 states in thread life cycle in java new, runnable, non-runnable and terminated. There is no running state.

    But for better understanding the threads, we are explaining it in the 5 states.

    Thread having below states.

    1. New State
    2. Ready State
    3. Running State
    4. Dead State
    5. Non-Runnable States (Blocked)
    life cycle of thread in java

    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 the 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:

    This is the state when the thread is still alive, but is currently not eligible to run.

    • 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 Thread sleeps for the 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.
    Practice Quiz 22 MCQs Smart Learning

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    MCQ Section

    MCQ 1
    Which of the following constructor of class Thread is valid one?
    MCQ 2
    When a class extends the Thread class, it should override ............ method of Thread class to start that thread.
    MCQ 3
    In java, a thread can be created by ..........
    MCQ 4
    What will be the output of the following program code? 
    public class Test implements Runnable{
        public static void main(String[] args){
                Thread t = new Thread(this);
                t.start();
        }

        public void run(){
                System.out.println("test");
        }
}
    MCQ 5
    Analyze the following code: 
    public abstract class Test implements Runnable{
        public void doSomething() { };
}
    MCQ 6
    What will happen after compiling and running following code? 
    class A implements Runnable{
      public void run(){
            System.out.println("run-a");
      }
}

1. public class Test{
2.       public static void main(String... args){
3.             A a = new A();
4.             Thread t = new Thread(a);
5.             t.start();
6.             t.start();
7.       }
8. }
    MCQ 7
    What will happen when you attempt to compile and run the following code? 
    1. public class Test extends Thread{
2.       public static void main(String argv[]){
3.             Test t = new Test();
4.             t.run();
5.             t.start();
6.       }
7.       public void run(){
8.             System.out.println("run-test");
9.       }
10. }
    MCQ 8
    What will be the output? 
    class One extends Thread{
	public void run(){
		for(int i=0; i<2; i++){
			System.out.print(i);
		}
	}
}

public class Test{
	public static void main(String args[]){
		Test t = new Test();
		t.call(new One());
	}
	
	public void call(One o){
		o.start();
	}
}
    MCQ 9
    Analyze the following code: 
    public class Test implements Runnable{
        public static void main(String[] args){
                Test t = new Test();
        }

        public Test(){
                Thread t = new Thread(this);
                t.start();
        }

        public void run(){
                System.out.println("test");
        }
}
    MCQ 10
    Analyze the following code: 
    public class Test implements Runnable{
        public static void main(String[] args){
                Test t = new Test();
                t.start();
        }

        public void run() { }
}
    MCQ 11
    What will be the output? 
    class A extends Thread{
      public void run(){
            for(int i=0; i<2; i++){
                  System.out.println(i);
            }
      }
}

public class Test{
      public static void main(String argv[]){
            Test t = new Test();
            t.check(new A(){});
      }
      public void check(A a){
            a.start();
      }
}
    MCQ 12
    What will happen when you attempt to compile and run the following code? 
    class A implements Runnable{
      public void run(){
            System.out.println("run-A");
      }
}

1. public class Test{
2.       public static void main(String argv[]){
3.             A a = new A();
4.             Thread t = new Thread(a);
5.             System.out.println(t.isAlive());
6.             t.start();
7.             System.out.println(t.isAlive());
8.       }
9. }
    MCQ 13
    Which of the following are methods of the Thread class?

    1) yield()
    2) sleep(long msec)
    3) go()
    4) stop()
    MCQ 14
    What notifyAll() method do?
    MCQ 15
    Predict the output: 
    class A implements Runnable{
      public void run(){
            try{
                  for(int i=0;i<4;i++){
                        Thread.sleep(100);
                        System.out.println(Thread.currentThread().getName());
                  }
            }catch(InterruptedException e){
            }
      }
}

public class Test{
      public static void main(String argv[]) throws Exception{
            A a = new A();
            Thread t = new Thread(a, "A");
            Thread t1 = new Thread(a, "B");
            t.start();
            t.join();
            t1.start();
      }
}
    MCQ 16
    What will be the output after compiling and executing the following code? 
    public class Test implements Runnable{
      public static void main(String[] args) throws InterruptedException{
            Thread a = new Thread(new Test());
            a.start();
            System.out.print("Begin");
            a.join();
            System.out.print("End");
      }
    
      public void run(){
            System.out.print("Run");
      }
}
    MCQ 17
    Predict the output: 
    public class Test extends Thread{
      private int i;
      public void run(){
            i++;
      }

      public static void main(String[] args){
            Test a = new Test();
            a.run();
            System.out.print(a.i);
            a.start();
            System.out.print(a.i);
      }
}
    MCQ 18
    What is the output for the below code? 
    class A implements Runnable{
      public void run(){
            System.out.println(Thread.currentThread().getName());
      }
}

1. public class Test{		
2.       public static void main(String... args){	
3.             A a = new A();
4.	       Thread t = new Thread(a);
5.	       t.setName("good");
6.	       t.start();
7.       }
8. }
    MCQ 19
    Which keyword when applied on a method indicates that only one thread should execute the method at a time.
    MCQ 20
    What is the output for the below code? 
    public class Test extends Thread{
      public static void main(String argv[]){
            Test t = new Test();
            t.run();
      }

      public void start(){
            for(int i = 0; i < 10; i++){
                  System.out.println("Value of i = " + i);
            }
      }
}
    MCQ 21
    What will be the output of the following program code? 
    public class Test implements Runnable{
      public void run(){
            System.out.print("go");
      }
    
      public static void main(String arg[]) {
            Thread t = new Thread(new Test());
            t.run();
            t.run();
            t.start();
      }
}
    MCQ 22
    Given the code. What will be the result? 
    public class Test implements Runnable{
      public static void main(String[] args) throws InterruptedException{
            Thread a = new Thread(new Test());
            a.start();
        
            System.out.print("Begin");
            a.join();
            System.out.print("End");
      }
    
      public void run(){
            System.out.print("Run");
      }
}