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Java Thread Join Examples
- Imagine the following scenario. You are preparing for tomorrow's final examination and feel a little hungry. So, you give your younger brother ten bucks and ask him to buy a pizza for you. In this case, you are the main thread and your brother is a child thread. Once your order is given, both you and your brother are doing their job concurrently (i.e., studying and buying a pizza). Now, we have two cases to consider. First, your brother brings your pizza back and terminates while you are studying. In this case, you can stop studying and enjoy the pizza. Second, you finish your study early and sleep (i.e., your assigned job for today - study for tomorrow's final exam - is done) before the pizza is available. Of course, you cannot sleep; otherwise, you won't have a chance to eat the pizza. What you are going to do is to wait until your brother brings the pizza back.
- A thread can execute a thread join to wait until the other thread terminates
- A parent thread may join with many child threads created by the parent. Or, a parent only join with some of its child threads, and ignore other child threads. In this case, those child threads that are ignored by the parent will be terminated when the parent terminates.
Thread Join Sample Code
| Code: |
package com.myjava.threads;
import java.util.ArrayList;
import java.util.List;
public class MyThreadJoin {
public static List<String> names = new ArrayList<String>();
public static void main(String a[]){
List<SampleThread> list = new ArrayList<SampleThread>();
for(int i=0;i<5;i++){
SampleThread s = new SampleThread();
list.add(s);
s.start();
}
for(SampleThread st:list){
try{
st.join();
} catch (Exception ex){}
}
System.out.println(names);
}
}
class SampleThread extends Thread{
public void run(){
for(int i=0; i<10; i++){
try{
Thread.sleep(10);
} catch(Exception ex){}
}
MyThreadJoin.names.add(getName());
}
}
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Example Output
[Thread-0, Thread-2, Thread-1, Thread-4, Thread-3]
Other Thread Examples
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String Vs StringBuffer
We know that String is immutable object. We can not change the value
of a String object once it is initiated. If we try to change the value of
the existing String object then it creates new object rather than changing
the value of the existing object. So incase, we are going to do more
modificatios on String, then use StringBuffer. StringBuffer updates the
existing objects value, rather creating new object.
If you don’t make mistakes, you’re not working on hard enough problems. And that’s a big mistake.
-- Frank Wilczek
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