Question

my goal is to generate a random number every 10 seconds and store in arraylist. when I generate the new number every 10 second I want to update the previous number from the arraylist. currently it gets the first number current num in main method but when I store after 10 second i'm not geting the update current number. NOTE: ***I want the Runnable to be in the arraylist method. Not in main method. my goal is to send the arraylist that has the update number***

import java.util.ArrayList;
import java.util.Random;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;

public class Main
{
public static void main(String[] args) throws Exception
{
  
ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
  
//schedule thread for evry 10 seconds
  
//executor.schedule(new sampleCallableExample(), 1, TimeUnit.MILLISECONDS);
executor.scheduleAtFixedRate(new sampleCallableExample(), 0, 10, TimeUnit.SECONDS);
System.out.println("array size:"+globals.Update.size());
for(int x=0;x {
  
System.out.println("Current Num = " + globals.Update.get(x));
  
}
  
}
}

import java.util.ArrayList;
public class globals
{
public static ArrayList Update = new ArrayList();
  
}

sampleCallableExample.java :

import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
import java.util.Random;
class sampleCallableExample implements Runnable
{
public static int genrand()
{
Random number = new Random();
//generate random number
int rand = number.nextInt(1000);
//return generated random number
return rand;
}
public Object call() throws Exception
{
//ArrayList Update = new ArrayList();
int CurrentNum = genrand();
System.out.println("generate number ==== " + CurrentNum);
globals.Update.clear();
globals.Update.add(CurrentNum);
System.out.println("Number added");
return globals.Update;
}

// As seen run wraps call object
public void run()
{
try
{
Object o = call();
//System.out.println("Returned " + o);
}
catch (Exception e)
{
e.printStackTrace();
}
}

public sampleCallableExample()
{
try
{
run();
  
  
}
catch(Exception e)
{
}
  
}
  
}   

Current Output:

generate number ==== 809

Number added

array size:1

Current Num = 809

generate number ==== 6

Number added

generate number ==== 107

Number added

It should be :

generate number ==== 809

Number added

array size:1

Current Num = 809

generate number ==== 6

Number added

array size:1

Current Num = 6

generate number ==== 107

Number added

array size:1

Current Num = 107

NOTE: ***I want the Runnable to be in the arraylist method. Not in main method. my goal is to send the arraylist that has the update number***I would apperciate any help.

Answer 1

Hi,

Please find the update code according to the sample output:

================================================

Main.java

================================================

import java.util.ArrayList;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class Main {
   public static void main(String[] args) throws Exception {

       ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);

//schedule thread for evry 10 seconds

//executor.schedule(new sampleCallableExample(), 1, TimeUnit.MILLISECONDS);
       executor.scheduleAtFixedRate(new sampleCallableExample(), 0, 10, TimeUnit.SECONDS);
   }
}

class globals {
   public static ArrayList Update = new ArrayList();

}

==============================================

sampleCallableExample.java

==============================================

import java.util.Random;

public class sampleCallableExample implements Runnable {
   public static int genrand() {
       Random number = new Random();
//generate random number
       int rand = number.nextInt(1000);
//return generated random number
       return rand;
   }

   public Object call() throws Exception {
//ArrayList Update = new ArrayList();
       int CurrentNum = genrand();
       System.out.println("generate number ==== " + CurrentNum);
       globals.Update.clear();
       globals.Update.add(CurrentNum);
       System.out.println("Number added");
       System.out.println("array size:" + globals.Update.size());
       System.out.println("Current Num = " + globals.Update.get(0));
       return globals.Update;
   }

// As seen run wraps call object
   public void run() {
       try {
           Object o = call();
//System.out.println("Returned " + o);
       } catch (Exception e) {
           e.printStackTrace();
       }
   }

   public sampleCallableExample() {
       try {
           run();

       } catch (Exception e) {
       }

   }

}

Sample output:

generate number ==== 478 Number added array size:1 Current Num = 478 generate number ==== 933 Number added array size:1 Current Num = 933 generate number ==== 415 Number added array size:1 Current Num = 415 generate number ==== 909 Number added array size: 1

I hope this helps you!!

Thanks