InstrumentingThreadPoolExecutor.java

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

public class InstrumentingThreadPoolExecutor extends ThreadPoolExecutor {

    private ThreadLocal<Long> startTime = new ThreadLocal<Long>();
    private long lastExecutionTime;
    private AtomicLong executionsCount = new AtomicLong();
    private AtomicLong executionsTime = new AtomicLong();

    public InstrumentingThreadPoolExecutor(int corePoolSize,
        int maximumPoolSize, long keepAliveTime, TimeUnit unit,
        BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory,
        RejectedExecutionHandler handler) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
    }

    @Override
    protected void beforeExecute(Thread t, Runnable r) {
        startTime.set(System.currentTimeMillis());
        super.beforeExecute(t, r);
    }

    @Override
    protected void afterExecute(Runnable r, Throwable t) {
        super.afterExecute(r, t);
        long execution = System.currentTimeMillis() - startTime.get();

        lastExecutionTime = execution;
        executionsCount.incrementAndGet();
        executionsTime.addAndGet(execution);
    }

    public long getLastExecutionTime() {
        return lastExecutionTime;
    }

    public long getExecutionsCount() {
        return executionsCount.get();
    }

    public long getExecutionsTime() {
        return executionsTime.get();
    }

}

InstrumentingThreadPoolExecutorImpl.java

import javax.management.NotCompliantMBeanException;
import javax.management.StandardMBean;

public class InstrumentingThreadPoolExecutorImpl extends StandardMBean implements InstrumentingThreadPoolExecutorMBean {

    private final InstrumentingThreadPoolExecutor instr;

    public InstrumentingThreadPoolExecutorImpl(InstrumentingThreadPoolExecutor instr) throws NotCompliantMBeanException {
        super(InstrumentingThreadPoolExecutorMBean.class);
        this.instr = instr;
    }

    @Override
    public long getExecutionsCount() {
        return instr.getExecutionsCount();
    }

    @Override
    public long getExecutionsTime() {
        return instr.getExecutionsTime();
    }

    @Override
    public long getLastExecutionTime() {
        return instr.getLastExecutionTime();
    }

    @Override
    public double getAverageExecutionTime() {
        return instr.getExecutionsTime() / instr.getExecutionsCount();
    }

    @Override
    public int getMaximumPoolSize() {
        return instr.getMaximumPoolSize();
    }

    @Override
    public int getActiveCount() {
        return instr.getActiveCount();
    }

}

InstrumentingThreadPoolExecutorMBean.java

public interface InstrumentingThreadPoolExecutorMBean {

    long getExecutionsCount();
    long getExecutionsTime();
    long getLastExecutionTime();
    double getAverageExecutionTime();

    int getMaximumPoolSize();
    int getActiveCount();

}