Calling a java class file which is scheduled using batch file but seems nothing happening

Question

Calling a java class file using batch file works fine.

Here is the code which is working.

public class TestA {

public static void main(String[] args) {
    new TestA().printA();
}

public void printA(){
    System.out.println("This is A...");
     try {
         File file = new File("D:/FileA.txt");
         boolean fvar = file.createNewFile();
         if (fvar){
              System.out.println("File has been created successfully");
         }
         else{
              System.out.println("File already present at the specified location");
         }
        } catch (IOException e) {
            System.out.println("Exception Occurred:");
            e.printStackTrace();
      }
}
}

The same above code if I put it on scheduling using task executors and try calling the same file using batch file, it's not working ( I mean here file creation is not happening). Need your help on this.

Code with scheduling:

public class TestD implements Runnable {

    private ScheduledExecutorService executor = null;

    @Override
    public void run() {
        try {
             File file = new File("D:/FileD.txt");
             boolean fvar = file.createNewFile();
             if (fvar){
                  System.out.println("File has been created successfully");
             }
             else{
                  System.out.println("File already present at the specified location");
             }
            } catch (IOException e) {
                System.out.println("Exception Occurred:");
                e.printStackTrace();
          }
    }

    public void executeScheduler() throws SQLException {
        executor.scheduleAtFixedRate(this, 2, 5, TimeUnit.SECONDS);
    }

    public static void main(String args[]){
        TestD testD = new TestD();
        try {
            testD.executeScheduler();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

I wrote the code to create a file just to test if my code is being called from the batch file or not, as I couldn't observe the system out statements which are shown in cmd prompt in a jiffy.

Edit:
The reason for this problem is due to NullPointerException but the exception is not able to capture as I'm calling the file using batch and the cmd window not showing the error or probably it's showing the error but not human capturable and window closes in fraction of a second. So I don't think this question is a duplicate of What is a NullPointerException, and how do I fix it?

You probably get a `NullPointerException` at the line `executor.scheduleAtFixedRate(this, 2, 5, TimeUnit.SECONDS);` since you never initialized `executor`. — , Mar 09 '18 at 10:46
thanks luk2302 & devpuh, this is because initialization not happened and I couldn't find it as I couldn't capture the log from cmd window. Added `executor = Executors.newScheduledThreadPool(1);` in the constructor and it started to work — Suresh, Mar 09 '18 at 10:54
May I know the reason why the 1 down vote to this question? I have provided all the necessary details seeking for help. Answer could be a silly or tough one but hope this is not the reason for the down vote. — Suresh, Mar 09 '18 at 10:59
You did not provide the exception + stacktrace, you simply stated "not working". — luk2302, Mar 09 '18 at 11:00
@luk2302 If I'm able to track the stacktrace, probably I would have solved the issue myself by looking at the exception. I also mentioned that I have written a code to create a file to check if my code is getting called or not. Hope I'm clear with myself. — Suresh, Mar 09 '18 at 11:02

score 0 · Accepted Answer · answered Mar 09 '18 at 11:19

The issue is due to the variable not initialized and throwing a NullPointerException which is not able to capture in my case. Added a constructor code to initialize the object and it started to work fine.

Modified Code which is working...

public class TestD implements Runnable {

    private ScheduledExecutorService executor = null;

    public TestC(){
        executor = Executors.newScheduledThreadPool(1);
    }

    @Override
    public void run() {
        try {
             File file = new File("D:/FileD.txt");
             boolean fvar = file.createNewFile();
             if (fvar){
                  System.out.println("File has been created successfully");
             }
             else{
                  System.out.println("File already present at the specified location");
             }
            } catch (IOException e) {
                System.out.println("Exception Occurred:");
                e.printStackTrace();
          }
    }

    public void executeScheduler() throws SQLException {
        executor.scheduleAtFixedRate(this, 2, 5, TimeUnit.SECONDS);
    }

    public static void main(String args[]){
        TestD testD = new TestD();
        try {
            testD.executeScheduler();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

Calling a java class file which is scheduled using batch file but seems nothing happening

1 Answers1