Using thread pool starting from java5

import java.util.concurrent.ExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;

/**
 * Processing jobs thread pool
 */
public class ProcessingJobExecutorService {
    private static ProcessingJobExecutorService _instance =null;
    private ExecutorService executorService;
   
    private ProcessingJobExecutorService(){
        executorService = new ScheduledThreadPoolExecutor(500);   
    }
   
    public static ProcessingJobExecutorService getInstance(){
        if(_instance==null){
            _instance=new ProcessingJobExecutorService();
        }
        return _instance;
    }
    public void execute (Runnable r){
        executorService.execute(r);
       
    }

}