MemoryStore

The MemoryStore class is simply an in-memory storage location for configuration files.

There is no hard persistence and is used primarily for testing purposes. However, the implementation provides a good idea on how stores work (especially the write method):

public class MemoryStore extends ConfigStore {

    // Some methods ommitted.

    private final ConcurrentHashMap cache = new ConcurrentHashMap();

    @Override /* ConfigStore */
    public synchronized String read(String name) {
        return emptyIfNull(cache.get(name));
    }

    @Override /* ConfigStore */
    public synchronized String write(String name, String expectedContents, String newContents) {

        // This is a no-op.
        if (isEquals(expectedContents, newContents))
            return null;

        String currentContents = read(name);

        if (expectedContents != null && ! isEquals(currentContents, expectedContents))
            return currentContents;

        update(name, newContents);

        // Success!
        return null;
    }

    @Override /* ConfigStore */
    public synchronized MemoryStore update(String name, String newContents) {
        cache.put(name, newContents);
        super.update(name, newContents);  // Trigger any listeners.
        return this;
    }
}