The join() method

The join() method waits for a thread to die. In other words, it causes the currently running threads to stop executing until the thread it joins with completes its task.

Syntax:

public void join()throws InterruptedException

public void join(long milliseconds)throws InterruptedException

Example of join() method

1. class TestJoinMethod1 extends Thread{  
2.  public void run(){  
3.   for(int i=1;i<=5;i++){  
4.    try{  
5.     Thread.sleep(500);  
6.    }catch(Exception e){System.out.println(e);}  
7.   System.out.println(i);  
8.   }  
9.  }  
10. public static void main(String args[]){  
11.  TestJoinMethod1 t1=new TestJoinMethod1();  
12.  TestJoinMethod1 t2=new TestJoinMethod1();  
13.  TestJoinMethod1 t3=new TestJoinMethod1();  
14.  t1.start();  
15.  try{  
16.   t1.join();  
17.  }catch(Exception e){System.out.println(e);}  
18.   
19.  t2.start();  
20.  t3.start();  
21.  }  
22. }  

Output:1
       2
       3
       4
       5
       1
       1
       2
       2
       3
       3
       4
       4
       5
       5

 

As you can see in the above example,when t1 completes its task then t2 and t3 starts executing.

Example of join(long miliseconds) method

1. class TestJoinMethod2 extends Thread{  
2.  public void run(){  
3.   for(int i=1;i<=5;i++){  
4.    try{  
5.     Thread.sleep(500);  
6.    }catch(Exception e){System.out.println(e);}  
7.   System.out.println(i);  
8.   }  
9.  }  
10. public static void main(String args[]){  
11.  TestJoinMethod2 t1=new TestJoinMethod2();  
12.  TestJoinMethod2 t2=new TestJoinMethod2();  
13.  TestJoinMethod2 t3=new TestJoinMethod2();  
14.  t1.start();  
15.  try{  
16.   t1.join(1500);  
17.  }catch(Exception e){System.out.println(e);}  
18.   
19.  t2.start();  
20.  t3.start();  
21.  }  
22. }  

Output:1
       2
       3
       1
       4
       1
       2
       5
       2
       3
       3
       4
       4
       5
       5

 

In the above example,when t1 is completes its task for 1500 miliseconds(3 times) then t2 and t3 starts executing.

---

getName(),setName(String) and getId() method:

public String getName()

public void setName(String name)

public long getId()

1. class TestJoinMethod3 extends Thread{  
2.   public void run(){  
3.    System.out.println("running...");  
4.   }  
5.  public static void main(String args[]){  
6.   TestJoinMethod3 t1=new TestJoinMethod3();  
7.   TestJoinMethod3 t2=new TestJoinMethod3();  
8.   System.out.println("Name of t1:"+t1.getName());  
9.   System.out.println("Name of t2:"+t2.getName());  
10.   System.out.println("id of t1:"+t1.getId());  
11.   
12.   t1.start();  
13.   t2.start();  
14.   
15.   t1.setName("Sonoo Jaiswal");  
16.   System.out.println("After changing name of t1:"+t1.getName());  
17.  }  
18. }  

Test it Now

Output:Name of t1:Thread-0
       Name of t2:Thread-1
       id of t1:8
       running...
       After changling name of t1:Sonoo Jaiswal
       running...
     
 

---

The currentThread() method:

The currentThread() method returns a reference to the currently executing thread object.

Syntax:

public static Thread currentThread()

Example of currentThread() method

1. class TestJoinMethod4 extends Thread{  
2.  public void run(){  
3.   System.out.println(Thread.currentThread().getName());  
4.  }  
5.  }  
6.  public static void main(String args[]){  
7.   TestJoinMethod4 t1=new TestJoinMethod4();  
8.   TestJoinMethod4 t2=new TestJoinMethod4();  
9.   
10.   t1.start();  
11.   t2.start();  
12.  }  
13. }  

Output:Thread-0
       Thread-1