'Back-End'에 해당되는 글 135건

Joining a thread

- join() waits for a thread to die

1. Syntax

- public void join()throws InterruptedException

- public void join(long milliseconds)throws InterruptedException

2. Example

public class join extends Thread{ public void run(){ for(int i = 0 ; i < 5; i++){ try{ Thread.sleep(500); }catch(Exception e){ System.out.println(e); } System.out.println(i); } } public static void main(String[]args){ join t1 = new join(); join t2 = new join(); join t3 = new join(); t1.start(); try{ t1.join(); }catch(Exception e){ System.out.println(e); } t2.start(); t3.start(); } }

Call a run() directly instead start()

- Each thread starts in a separate call stack, like this

- Invoking the run() from main thread, the run() method goes onto the current call stack 

1. Problem

public class directRn extends Thread{ public void run(){ for(int i = 0; i<5;i++){ try{ Thread.sleep(500); }catch(InterruptedException e){ System.out.println(e); } System.out.println(i); } } public static void main(String[]args){ directRn t1 = new directRn(); directRn t2 = new directRn(); t1.run(); t2.run(); } }

- There is no context-switching 

- t1 and t2 will be treated as normal object not thread object

Sleeping a thread

- It is used to sleep a thread for the specified amount of time

1. Syntax

- public static void sleep(long miliseconds)throws InterruptedExceptioin

- public static void sleep(long miliseconds, int nanos)throws InterruptedException

2. Example

public class Sleeping extends Thread{ public void run(){ for(int i = 1; i<5;i++){ try{ Thread.sleep(500); }catch(InterruptedException e){ System.out.println(e); } System.out.println(i); } } public static void main(String[]args){ Sleeping t1 =new Sleeping(); Sleeping t2 =new Sleeping(); t1.start(); t2.start(); } }

- At a time only one thread is executed

- If you sleep a thread for the specified time, the thread schedular pick up another thread

Thread Scheduler

1. What is it?

- Thread scheduler is the part of the JVM that decides which thread should run

- Only one thread at a time can run in a single process

- The Thread scheduler mainly uses preemptive or time slicing scheduling to schedule the threads

2. Different between preemptive and time slicing

1) preemptive

- The highest priority task executes until it enters the waiting or dead states

- A higher priority task comes into existence

2) time slicing

- A task executes for a predefined slice of time and then reenters the pool of ready tasks

- The scheduler then determines which task should execute next, based on priority and other factors