Ytdyklly

I am trying to come up with design for different types of cache with different eviction policies but I am facing difficulty linking the eviction policy with cache. Mainly what to pass in evict() method so that it can be generic for different cache implementations like LRU, LFU etc.

It will really helpful if this can be reviewed and I get some pointers on how to do it.

Here's what I have worked upon till now:

Cache.java

public interface Cache {



    String get(String key);



    boolean set(String key, String value);



    void evict();



    EvictionPolicy getEvictionPolicy();



    void startEvictor(long delay);

}

EvictionPolicy

public interface EvictionPolicy {

    //Scheduled execution of this method examines the cache key

    //if it can be evicted return true else false

    boolean evict();

}

CacheConfig.java

public class CacheConfig {



    private EvictionPolicy evictionPolicy;



    public EvictionPolicy getEvictionPolicy() {

        return evictionPolicy;

    }



    public void setEvictionPolicy(EvictionPolicy evictionPolicy) {

        this.evictionPolicy = evictionPolicy;

    }

}

BaseCache.java

import java.util.concurrent.ScheduledThreadPoolExecutor;

import java.util.concurrent.ThreadFactory;

import java.util.concurrent.TimeUnit;



public class BaseCache implements Cache{



    private volatile EvictionPolicy evictionPolicy;



    private Evictor evictor = null;



    public BaseCache(CacheConfig config) {

        setConfig(config);

    }



    public void setConfig(CacheConfig config){

        setEvictionPolicy(config.getEvictionPolicy());

    }



    public void setEvictionPolicy(final EvictionPolicy evictionPolicy) {

        this.evictionPolicy = evictionPolicy;

    }



    @Override

    public void evict() {

        EvictionPolicy evictionPolicy = getEvictionPolicy();

        evictionPolicy.evict();

    }



    @Override

    public EvictionPolicy getEvictionPolicy() {

        return evictionPolicy;

    }



    @Override

    public String get(String key) {

        return null;

    }



    @Override

    public boolean set(String key, String value) {

        return false;

    }



    public void startEvictor(final long delay) {

        if (delay > 0) {

            evictor = new Evictor();

            ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(1, new EvictorThreadFactory());

            executor.scheduleWithFixedDelay(evictor, delay, delay, TimeUnit.MILLISECONDS);

        }

    }



    class Evictor implements Runnable {



        @Override

        public void run() {

            try {

                evict();

            } catch(final Exception e) {

                System.out.println("Swallow exception!!");

            }

        }

    }



    private static class EvictorThreadFactory implements ThreadFactory {



        @Override

        public Thread newThread(final Runnable runnable) {

            return new Thread(null, runnable, "evictor-thread");

        }

    }

}

DefaultEvictionPolicy

 public class DefaultEvictionPolicy implements EvictionPolicy {



    @Override

    public boolean evict() {

        return true;

    }

}

LruCache

public class LruCache extends BaseCache {



    private Map<String, String> cachedObjects = new ConcurrentHashMap<>();



    public LruCache(CacheConfig config) {

        super(config);

        setConfig(config);

    }



    public void setConfig(CacheConfig config){

        super.setConfig(config);

        setEvictionPolicy(config.getEvictionPolicy());

    }



    @Override

    public void evict() {

        EvictionPolicy evictionPolicy = getEvictionPolicy();

        evictionPolicy.evict();

    }





    @Override

    public String get(String key) {

        return null;

    }



    @Override

    public boolean set(String key, String value) {

        return false;

    }

}

Main.java

public class Main {

    public static void main(String args) {



        CacheConfig config = new CacheConfig();

        config.setEvictionPolicy(new DefaultEvictionPolicy());



        Cache cache = new LruCache(config);



        cache.set("key1", "10");

        cache.set("key2", "12");

        cache.get("key1");

        cache.startEvictor(5);

    }

}