First of all To understand this Post You must have some quite good knowledge about the Threads and their behaviors.
Now lets talk about the topic. What is a Preemptive thread scheduler? And why we need it?. The Preemptive scheduler means can suspend a current running thread and run another read and RESUME the previous suspended thread to continue.
So why we need a Preemptive task scheduler. In java JVM(java virtual machine ) has a thread scheduler but it is non preemptive scheduler. So if we need a some kind of Preemptive thread scheduler we have to build it. And we can't control massive complex systems with a non preemptive thread scheduler.
So lets see how can we build a preemptive task scheduler.
First of all we have to maintain a thread list that we are going to manage. It can be a vector , stack or array of threads or a queue. The characteristics of the scheduler will depend on the storing system of the thread list.We need to update a variable(type of thread ) to store the current thread which is at the running state for a given instance. And we must have a method to get the next thread to run.
In this scenario the preemptive thread scheduler it self is a thread which has the highest priority among the handling threads. So it can suspend or pause a any thread because it has the high priority than other threads.
Now Let see a sample code written in java to create a preemptive thread scheduler.
Now lets talk about the topic. What is a Preemptive thread scheduler? And why we need it?. The Preemptive scheduler means can suspend a current running thread and run another read and RESUME the previous suspended thread to continue.
So why we need a Preemptive task scheduler. In java JVM(java virtual machine ) has a thread scheduler but it is non preemptive scheduler. So if we need a some kind of Preemptive thread scheduler we have to build it. And we can't control massive complex systems with a non preemptive thread scheduler.
So lets see how can we build a preemptive task scheduler.
First of all we have to maintain a thread list that we are going to manage. It can be a vector , stack or array of threads or a queue. The characteristics of the scheduler will depend on the storing system of the thread list.We need to update a variable(type of thread ) to store the current thread which is at the running state for a given instance. And we must have a method to get the next thread to run.
In this scenario the preemptive thread scheduler it self is a thread which has the highest priority among the handling threads. So it can suspend or pause a any thread because it has the high priority than other threads.
Now Let see a sample code written in java to create a preemptive thread scheduler.
import java.util.Scanner;
import java.util.Vector;
import java.util.*;
public class PreemtiveThreadShedular extends Thread{
private Vector taskList=new Vector(5,5);
private Philosopher currentThread;
private int index=0;
public static void main(String [] args){
PreemtiveThreadShedular shedular=new PreemtiveThreadShedular();
shedular.initializeThreads();
shedular.start();
shedular.run();
}
public PreemtiveThreadShedular(){
this.setPriority(MAX_PRIORITY);
}
public void initializeThreads(){
Philosopher [] phi=new Philosopher[num];
for(int i=0;i<phi.length;i++){
phi[i]=new Philosopher(""+i);
phi[i].setPriority(NORM_PRIORITY);
phi[i].start();
phi[i].suspend();
taskList.add(phi[i]);
}
}
public void nextThread(){
int size=taskList.size();
if(taskList.elementAt(index)!=null){
currentThread=(Philosopher) taskList.elementAt(index);
currentThread.suspend();
}
index++;
if(index==size){
index=0;
}
currentThread=(Philosopher) taskList.elementAt(index);
currentThread.resume();
try{
currentThread.run();
}
catch(InterruptedException e){
System.out.println("Interrupted Error Occured....");
}
}
public void run(){
while(isAlive()){
nextThread();
try{
sleep(100);
}
catch(InterruptedException e){
System.out.println("Error occured While Interrupting....");
stop();
}
}
}
}
class Philosopher extends Thread{
private String name;
public Philosopher(String name){
this.name=name;
}
public void run(){
System.out.println(name+" Thread is running");
}
}
