PriorityExecutor.java

package com.linkedin.camus.sweeper.utils;

import java.util.Comparator;
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
import java.util.concurrent.PriorityBlockingQueue;
import java.util.concurrent.RunnableFuture;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;


public class PriorityExecutor extends ThreadPoolExecutor {
  public PriorityExecutor(int poolsize) {
    super(poolsize, poolsize, 60L, TimeUnit.SECONDS, new PriorityBlockingQueue<Runnable>(300,
        new PriorityTaskComparator()));
  }

  @Override
  protected <T> RunnableFuture<T> newTaskFor(final Callable<T> callable) {
    if (callable instanceof Important)
      return new PriorityTask<T>(((Important) callable).getPriority(), callable);
    else
      return new PriorityTask<T>(0, callable);
  }

  @Override
  protected <T> RunnableFuture<T> newTaskFor(final Runnable runnable, final T value) {
    if (runnable instanceof Important)
      return new PriorityTask<T>(((Important) runnable).getPriority(), runnable, value);
    else
      return new PriorityTask<T>(0, runnable, value);
  }

  public interface Important {
    int getPriority();
  }

  private static final class PriorityTask<T> extends FutureTask<T> implements Comparable<PriorityTask<T>> {
    private final int priority;

    public PriorityTask(final int priority, final Callable<T> tCallable) {
      super(tCallable);

      this.priority = priority;
    }

    public PriorityTask(final int priority, final Runnable runnable, final T result) {
      super(runnable, result);

      this.priority = priority;
    }

    @Override
    public int compareTo(final PriorityTask<T> o) {
      final long diff = o.priority - priority;
      return 0 == diff ? 0 : 0 > diff ? -1 : 1;
    }
  }

  private static class PriorityTaskComparator implements Comparator<Runnable> {
    @Override
    public int compare(final Runnable left, final Runnable right) {
      return ((PriorityTask) left).compareTo((PriorityTask) right);
    }
  }
}