Config.java

package com.tectonica;

import org.yaml.snakeyaml.DumperOptions;
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.constructor.Constructor;
import org.yaml.snakeyaml.nodes.Tag;

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

/**
 * This is a general purpose YAML-based configuration file. To use it, add this to your <code>pom.xml</code>:
 * <pre>
 * &lt;dependency&gt;
 *     &lt;groupId&gt;org.yaml&lt;/groupId&gt;
 *     &lt;artifactId&gt;snakeyaml&lt;/artifactId&gt;
 *     &lt;version&gt;1.19&lt;/version&gt;
 * &lt;/dependency&gt;
 * </pre>
 * <p>
 * Use {@link #get()} to retrieve the in-memory copy of the configuration object. If you change it, be sure to call
 * {@link #save()} after all changes are done.
 *
 * @author Zach Melamed
 * @since 11/5/2017
 */
public class Config {

    private static final File configFile = new File(System.getProperty("user.home"), ".my-app");

    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    //
    // CONFIGURATION MEMBERS + DEFAULT VALUES
    //
    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////

    public double width = 1000.0;
    public double height = 700.0;
    public Double x = null; // implementation allows NULL, means auto-detect
    public Double y = null; // implementation allows NULL, means auto-detect
    public String csvFile = "./src/test/resources";
    public String referenceFolder = "";

    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    //
    // APIs
    //
    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////

    private static final Yaml yaml = new Yaml(new Constructor(Config.class));
    private static Config config = null;

    public static Config get() {
        if (config == null) {
            load();
        }
        return config;
    }

    public static void save() {
        try (FileWriter writer = new FileWriter(configFile)) {
            writer.write(yaml.dumpAs(config, Tag.MAP, DumperOptions.FlowStyle.BLOCK));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static void load() {
        try (FileReader reader = new FileReader(configFile)) {
            config = yaml.loadAs(reader, Config.class);
            if (config == null) { // empty file
                config = new Config();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}