poc.java

import android.content.Context;

import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.model.LatLng;
import com.google.maps.android.clustering.ClusterItem;
import com.google.maps.android.collections.MarkerManager;

import java.util.Collection;
import java.util.Set;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;


// contracts for getting required info out of T
interface LatLngGetter<T>{
    LatLng get(T t);
}

interface TitleGetter<T>{
    String get(T t);
}

interface SnippetGetter<T>{
    String get(T t);
}

// concrete implementation for ClusterItem getters
class ClusterItemLatLngGetter<T extends ClusterItem> implements LatLngGetter<T>{
    @Override
    public LatLng get(T clusterItem) {
        return clusterItem.getPosition();
    }
}

class ClusterItemTitleGetter<T extends ClusterItem> implements TitleGetter<T>{
    @Override
    public String get(T clusterItem) {
        return clusterItem.getTitle();
    }
}

class ClusterItemSnippetGetter<T extends ClusterItem> implements SnippetGetter<T>{
    @Override
    public String get(T clusterItem) {
        return clusterItem.getSnippet();
    }
}

public class ClusterManager<T> implements
        GoogleMap.OnCameraIdleListener,
        GoogleMap.OnMarkerClickListener,
        GoogleMap.OnInfoWindowClickListener {

    public ClusterManager(Context context, GoogleMap map, MarkerManager markerManager, LatLngGetter<T> latLngGetter, TitleGetter<T> titleGetter, SnippetGetter<T> snippetGetter) {
        // ...
    }

    public ClusterManager(Context context, GoogleMap map, LatLngGetter<T> latLngGetter, TitleGetter<T> titleGetter, SnippetGetter<T> snippetGetter) {
        this(context, map, new MarkerManager(map), latLngGetter, titleGetter, snippetGetter);
    }


    public static <T extends ClusterItem>ClusterManager<T> factory(Context context, GoogleMap map){
        return new ClusterManager<>(
                context,
                map,
                new ClusterItemLatLngGetter<>(),
                new ClusterItemTitleGetter<>(),
                new ClusterItemSnippetGetter<>()
        );
    }

    public interface OnClusterClickListener<T> {
        boolean onClusterClick(Cluster<T> cluster);
    }

    public interface OnClusterInfoWindowClickListener<T> {
        void onClusterInfoWindowClick(Cluster<T> cluster);
    }

    public interface OnClusterInfoWindowLongClickListener<T> {
        void onClusterInfoWindowLongClick(Cluster<T> cluster);
    }

    public interface OnClusterItemClickListener<T> {
        boolean onClusterItemClick(T item);
    }

    public interface OnClusterItemInfoWindowClickListener<T> {
        void onClusterItemInfoWindowClick(T item);
    }

    public interface OnClusterItemInfoWindowLongClickListener<T> {
        void onClusterItemInfoWindowLongClick(T item);
    }
}

public class NonHierarchicalDistanceBasedAlgorithm<T> extends AbstractAlgorithm<T> {
    NonHierarchicalDistanceBasedAlgorithm(LatLngGetter<T> latLngGetter){
        // ...
    }
    // use the latLngGetter.get(T) to get latLng
    
    // from getClusters method:
    // StaticCluster<T> cluster = new StaticCluster<>(latLngGetter.get(candidate.mClusterItem));

    // if needed static NonHierarchicalDistanceBasedAlgorithm<T extends ClusterItem> factory() can be provided
    // in same manner as with ClusterManager
}

public abstract class AbstractAlgorithm<T> implements Algorithm<T> {

    private final ReadWriteLock mLock = new ReentrantReadWriteLock();

    @Override
    public void lock() {
        mLock.writeLock().lock();
    }

    @Override
    public void unlock() {
        mLock.writeLock().unlock();
    }
}

public interface Algorithm<T> {
    boolean addItem(T item);
    boolean addItems(Collection<T> items);
    void clearItems();
    boolean removeItem(T item);
    boolean updateItem(T item);
    boolean removeItems(Collection<T> items);
    Set<? extends Cluster<T>> getClusters(float zoom);
    Collection<T> getItems();
    void setMaxDistanceBetweenClusteredItems(int maxDistance);
    int getMaxDistanceBetweenClusteredItems();
    void lock();
    void unlock();
}


public class DefaultClusterRenderer<T> implements ClusterRenderer<T>{
    public DefaultClusterRenderer(Context context, GoogleMap map, ClusterManager<T> clusterManager, LatLngGetter<T> latLngGetter, TitleGetter<T> titleGetter, SnippetGetter<T> snippetGetter){
        // ...
    }

    // use the latLngGetter.get(T) to get latLng
    // use the titleGetter.get(T) to get title
    // use the snippetGetter.get(T) to get snippet
}

public interface Cluster<T> {
    LatLng getPosition();
    Collection<T> getItems();
    int getSize();
}


public interface ClusterRenderer<T> {
    void onClustersChanged(Set<? extends Cluster<T>> clusters);
    void setOnClusterClickListener(ClusterManager.OnClusterClickListener<T> listener);
    void setOnClusterInfoWindowClickListener(ClusterManager.OnClusterInfoWindowClickListener<T> listener);
    void setOnClusterInfoWindowLongClickListener(ClusterManager.OnClusterInfoWindowLongClickListener<T> listener);
    void setOnClusterItemClickListener(ClusterManager.OnClusterItemClickListener<T> listener);
    void setOnClusterItemInfoWindowClickListener(ClusterManager.OnClusterItemInfoWindowClickListener<T> listener);
    void setOnClusterItemInfoWindowLongClickListener(ClusterManager.OnClusterItemInfoWindowLongClickListener<T> listener);
    void setAnimation(boolean animate);
    void onAdd();
    void onRemove();
}