一种基于单例模式的任务线程池工具类

import java.util.concurrent.Callable;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadPoolExecutor;

import lombok.extern.slf4j.Slf4j;

/**
 * task线程池的工具类(单例)13  *
 * 2020年02月26日
 * @param
 */
@Slf4j
public class ThreadPoolManager {
    
    
    private static final int THREAD_POOL_SIZE = 8;
    
    /**
     * 非核心线程闲置时超时1s
     */
    private static final int KEEP_ALIVE = 1;
    
    private static ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newFixedThreadPool(THREAD_POOL_SIZE);
    
    private ThreadPoolManager() {
    }
    
    private static class SingletonInner {
        private static ThreadPoolManager instance = new ThreadPoolManager();
    }
    
    public static ThreadPoolManager getInstance() {
         return SingletonInner.instance;
    }
    
     /**
     * 开启一个无返回结果的线程
     * @param r
     */
    public void execute(Runnable runnable) {
        log.info("start a thread ->" + Thread.currentThread().getName());
        // 把一个任务丢到了线程池中
        executor.execute(runnable);
    }

    /**
     * 开启一个有返回结果的线程
     * @param runnable
     * @return
     */
    public <T> Future<T> submit(Callable<T> runnable) {
        // 把一个任务丢到了线程池中
        return executor.submit(runnable);
    }
 
    /**
     * 把任务移除等待队列
     * @param runnable
     */
    public void cancel(Runnable runnable) {
        if (runnable != null) {
            executor.getQueue().remove(runnable);
        }
    }
    
    /**
     * 获取空闲线程数
     * @return
     */
    public static int getFreeThreadNum() {
        int freeNum = executor.getCorePoolSize() -executor.getActiveCount();
        return freeNum;
    }
    
}