Java - Threads isAlive()

The thread class provides a method which can be called on an instance of a Thread to determine if it is currently executing. If isAlive() returns false the thread is either a new thread that is not currently executing or it is dead.

public boolean isAlive();

The following code creates a thread and executes it by calling it's start() method. Before the thread is started a test is performed to determine if the thread is currently executing. Since the thread is new, isAlive() returns false. You will also notice within the run() method a reference to the current thread is grabbed using the following method.

Code:

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static Thread currentThread()

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Since isAlive() is called within the run() method isAlive() returns true because the thread is executing at that time.

Code:

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public class ThreadTest{
 public static void main(String[] args){
  T t = new T("T Thread");
  threadStatus(t.isAlive(),t.getName());
  t.start();
 }
 public static void threadStatus(boolean isalive, String tname){
  String status = isalive ? "is alive" : " is not alive";
  System.out.println(tname +""+  status);
 }
}

class T extends Thread{
 public T(String tname){
  super(tname);
 }
 public void run(){
  Thread t = Thread.currentThread();
  String tname = t.getName(); 
  boolean isalive = t.isAlive();
  for(int i = 0; i < 9; ++i){
  System.out.println(tname + " is alive ?" + " : " + isalive);
  }
 }
}

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