我创建了一个countminsketch来计算一些值的最小频率。我正在使用executorservice异步更新草图。我在我的flink项目中使用这个类，它需要是可序列化的，所以我实现了可序列化接口。但是，这还不够，因为executorservice还需要可序列化。如何以可序列化的方式使用executorservice？或者executorservice是否有可序列化的实现？

import java.io.Serializable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class CountMinSketch implements Serializable {

    private static final long serialVersionUID = 1123747953291780413L;

    private static final int H1 = 0;
    private static final int H2 = 1;
    private static final int H3 = 2;
    private static final int H4 = 3;
    private static final int LIMIT = 100;
    private final int[][] sketch = new int[4][LIMIT];

    final NaiveHashFunction h1 = new NaiveHashFunction(11, 9);
    final NaiveHashFunction h2 = new NaiveHashFunction(17, 15);
    final NaiveHashFunction h3 = new NaiveHashFunction(31, 65);
    final NaiveHashFunction h4 = new NaiveHashFunction(61, 101);

    private ExecutorService executor = Executors.newSingleThreadExecutor();

    public CountMinSketch() {
        // initialize sketch
    }

    public Future<Boolean> updateSketch(String value) {
        return executor.submit(() -> {
            sketch[H1][h1.getHashValue(value)]++;
            sketch[H2][h2.getHashValue(value)]++;
            sketch[H3][h3.getHashValue(value)]++;
            sketch[H4][h4.getHashValue(value)]++;
            return true;
        });
    }

    public Future<Boolean> updateSketch(String value, int count) {
        return executor.submit(() -> {
            sketch[H1][h1.getHashValue(value)] = sketch[H1][h1.getHashValue(value)] + count;
            sketch[H2][h2.getHashValue(value)] = sketch[H2][h2.getHashValue(value)] + count;
            sketch[H3][h3.getHashValue(value)] = sketch[H3][h3.getHashValue(value)] + count;
            sketch[H4][h4.getHashValue(value)] = sketch[H4][h4.getHashValue(value)] + count;
            return true;
        });
    }

    public int getFrequencyFromSketch(String value) {
        int valueH1 = sketch[H1][h1.getHashValue(value)];
        int valueH2 = sketch[H2][h2.getHashValue(value)];
        int valueH3 = sketch[H3][h3.getHashValue(value)];
        int valueH4 = sketch[H4][h4.getHashValue(value)];
        return findMinimum(valueH1, valueH2, valueH3, valueH4);
    }

    private int findMinimum(final int a, final int b, final int c, final int d) {
        return Math.min(Math.min(a, b), Math.min(c, d));
    }
}

import java.io.Serializable;

public class NaiveHashFunction implements Serializable {

    private static final long serialVersionUID = -3460094846654202562L;
    private final static int LIMIT = 100;
    private long prime;
    private long odd;

    public NaiveHashFunction(final long prime, final long odd) {
        this.prime = prime;
        this.odd = odd;
    }

    public int getHashValue(final String value) {
        int hash = value.hashCode();
        if (hash < 0) {
            hash = Math.abs(hash);
        }
        return calculateHash(hash, prime, odd);
    }

    private int calculateHash(final int hash, final long prime, final long odd) {
        return (int) ((((hash % LIMIT) * prime) % LIMIT) * odd) % LIMIT;
    }
}

flink等级：

public static class AverageAggregator implements
            AggregateFunction<Tuple3<Integer, Tuple5<Integer, String, Integer, String, Integer>, Double>, Tuple3<Double, Long, Integer>, Tuple2<String, Double>> {

        private static final long serialVersionUID = 7233937097358437044L;
        private String functionName;
        private CountMinSketch countMinSketch = new CountMinSketch();
.....
}

错误：

Exception in thread "main" org.apache.flink.api.common.InvalidProgramException: The implementation of the AggregateFunction is not serializable. The object probably contains or references non serializable fields.
    at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:99)
    at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.clean(StreamExecutionEnvironment.java:1559)
    at org.apache.flink.streaming.api.datastream.WindowedStream.aggregate(WindowedStream.java:811)
    at org.apache.flink.streaming.api.datastream.WindowedStream.aggregate(WindowedStream.java:730)
    at org.apache.flink.streaming.api.datastream.WindowedStream.aggregate(WindowedStream.java:701)
    at org.sense.flink.examples.stream.MultiSensorMultiStationsReadingMqtt2.<init>(MultiSensorMultiStationsReadingMqtt2.java:39)
    at org.sense.flink.App.main(App.java:141)
Caused by: java.io.NotSerializableException: java.util.concurrent.Executors$FinalizableDelegatedExecutorService
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
    at org.apache.flink.util.InstantiationUtil.serializeObject(InstantiationUtil.java:534)
    at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:81)
    ... 6 more