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Preferences utilities.

There is a newer version: 0.9.0

package cdc.util.prefs;

import java.io.File;
import java.util.prefs.Preferences;
import java.util.prefs.PreferencesFactory;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

/**
 * PreferencesFactory implementation that stores the preferences in a user-defined file.
 * 
 * To use it, set the system property {@code java.util.prefs.PreferencesFactory} to
 * {@code cdc.util.prefs.FilePreferencesFactory}.
 */
public class FilePreferencesFactory implements PreferencesFactory {
    private static final Logger LOGGER = LogManager.getLogger(FilePreferencesFactory.class);
    private static File preferencesFile;

    private Preferences rootPreferences = null;

    public FilePreferencesFactory() {
        LOGGER.trace("()");
    }

    @Override
    public Preferences systemRoot() {
        return userRoot();
    }

    @Override
    public Preferences userRoot() {
        if (rootPreferences == null) {
            LOGGER.trace("Instantiate root preferences");

            rootPreferences = new FilePreferences(null, "");
        }
        return rootPreferences;
    }

    public static File getPreferencesFile() {
        if (preferencesFile == null) {
            final String filename = System.getProperty("user.home") + File.separator + ".fileprefs";
            preferencesFile = new File(filename).getAbsoluteFile();
            LOGGER.info("Set preferences file to {}", preferencesFile);
        }
        return preferencesFile;
    }
}